chore: Update discovery artifacts (#1425)

## Deleted keys were detected in the following stable discovery artifacts:
admin directory_v1 https://github.com/googleapis/google-api-python-client/commit/1534f8926019f43dc87a29c1ca32191884556e3b
bigquery v2 https://github.com/googleapis/google-api-python-client/commit/59c51e319602741632201d2ce61a6b03f13e4003
file v1 https://github.com/googleapis/google-api-python-client/commit/0cd409a2d15c68aca3ea864400fc4772b9b4e503
memcache v1 https://github.com/googleapis/google-api-python-client/commit/665ce5b47b9b3238dcfa201b9343bf6447df5994
youtube v3 https://github.com/googleapis/google-api-python-client/commit/5046950872559fe93b954dc9a4f71fd724176247

## Deleted keys were detected in the following pre-stable discovery artifacts:
analyticsadmin v1alpha https://github.com/googleapis/google-api-python-client/commit/934358e5c041ffd1449e7c744463e61e94381ed5
documentai v1beta3 https://github.com/googleapis/google-api-python-client/commit/e8aaabbc7670aefc4a745916fccb31424745f748
file v1beta1 https://github.com/googleapis/google-api-python-client/commit/0cd409a2d15c68aca3ea864400fc4772b9b4e503
memcache v1beta2 https://github.com/googleapis/google-api-python-client/commit/665ce5b47b9b3238dcfa201b9343bf6447df5994
networkconnectivity v1alpha1 https://github.com/googleapis/google-api-python-client/commit/2cc462638aec61f4e775bfce883e725b104eeabb

## Discovery Artifact Change Summary:
feat(admin): update the api https://github.com/googleapis/google-api-python-client/commit/1534f8926019f43dc87a29c1ca32191884556e3b
feat(alertcenter): update the api https://github.com/googleapis/google-api-python-client/commit/7a488d3f0deef3e1f106cff63b1e4f66ad1727bb
feat(analyticsadmin): update the api https://github.com/googleapis/google-api-python-client/commit/934358e5c041ffd1449e7c744463e61e94381ed5
feat(analyticsdata): update the api https://github.com/googleapis/google-api-python-client/commit/40f712130674cec09c1dd7560f69a330a335b226
feat(androiddeviceprovisioning): update the api https://github.com/googleapis/google-api-python-client/commit/81a0002a7051aeab647a3296fb18ce7973bf7137
feat(apigee): update the api https://github.com/googleapis/google-api-python-client/commit/2e6c78a93b2c0ee7001eb163ec95f9afc8f35575
feat(appengine): update the api https://github.com/googleapis/google-api-python-client/commit/125f74a61a94af17c01930841a79db46d3a059c5
feat(bigquery): update the api https://github.com/googleapis/google-api-python-client/commit/59c51e319602741632201d2ce61a6b03f13e4003
feat(cloudasset): update the api https://github.com/googleapis/google-api-python-client/commit/e615264971ccee6eb9b450fe3d85614209c0fee8
feat(cloudbuild): update the api https://github.com/googleapis/google-api-python-client/commit/ceddaccf23eb8b809688907cfdef8906cd77d65d
feat(cloudidentity): update the api https://github.com/googleapis/google-api-python-client/commit/22cd08b69b034c2cdfd854e1ac784f834539db3a
feat(container): update the api https://github.com/googleapis/google-api-python-client/commit/f494c63a42dc418559292c6269289317d9cebc23
feat(documentai): update the api https://github.com/googleapis/google-api-python-client/commit/e8aaabbc7670aefc4a745916fccb31424745f748
feat(drive): update the api https://github.com/googleapis/google-api-python-client/commit/72cab88ce591d906ea1cfcbe4dee354cccb623f2
feat(file): update the api https://github.com/googleapis/google-api-python-client/commit/0cd409a2d15c68aca3ea864400fc4772b9b4e503
feat(firebaseappcheck): update the api https://github.com/googleapis/google-api-python-client/commit/9a0131b2326327109d1ba7af97b1f4808dd7a898
feat(healthcare): update the api https://github.com/googleapis/google-api-python-client/commit/45ee6b28b86a43f44c707e15a7e06fdf8fce6a0f
feat(ideahub): update the api https://github.com/googleapis/google-api-python-client/commit/73b86d9d37f33aeaed74772d0319ba1350e54ed5
feat(managedidentities): update the api https://github.com/googleapis/google-api-python-client/commit/a07ed4558c93cb8f7fae49c7b353f46ccfea6c10
feat(memcache): update the api https://github.com/googleapis/google-api-python-client/commit/665ce5b47b9b3238dcfa201b9343bf6447df5994
feat(metastore): update the api https://github.com/googleapis/google-api-python-client/commit/9fd5ffbf37fb052323f5fa68d307c68391c519ac
feat(ml): update the api https://github.com/googleapis/google-api-python-client/commit/cf54d564915a558569c093287b448a7819e215f6
feat(monitoring): update the api https://github.com/googleapis/google-api-python-client/commit/d1ffbfc041f23f904cd8bc35a450871b2909473b
feat(networkconnectivity): update the api https://github.com/googleapis/google-api-python-client/commit/2cc462638aec61f4e775bfce883e725b104eeabb
feat(notebooks): update the api https://github.com/googleapis/google-api-python-client/commit/831ba938855aa4bdefafedf63e01af43350e7ed2
feat(ondemandscanning): update the api https://github.com/googleapis/google-api-python-client/commit/c04b4023477393cbb41984b14e0c734fc8587d45
feat(paymentsresellersubscription): update the api https://github.com/googleapis/google-api-python-client/commit/2cd5b1c2ef524f3ab00630508710cce7bee53574
feat(prod_tt_sasportal): update the api https://github.com/googleapis/google-api-python-client/commit/8b6bd24e57a79f470c750ad04052f79a3cafe0fa
feat(realtimebidding): update the api https://github.com/googleapis/google-api-python-client/commit/fd514dc8d86182dc17698f3293144928535f709c
feat(reseller): update the api https://github.com/googleapis/google-api-python-client/commit/20226c4401956732772e2a563c7920666135e605
feat(sasportal): update the api https://github.com/googleapis/google-api-python-client/commit/38d5156350b79a9933b2806f4bbe443043a33185
feat(sts): update the api https://github.com/googleapis/google-api-python-client/commit/190e13ebe5a4660d8825d3a8708559077a342bdf
feat(transcoder): update the api https://github.com/googleapis/google-api-python-client/commit/fbcacce6a17c1cae45b22f4a2058e730ec84b55a
feat(youtube): update the api https://github.com/googleapis/google-api-python-client/commit/5046950872559fe93b954dc9a4f71fd724176247
diff --git a/googleapiclient/discovery_cache/documents/gmail.v1.json b/googleapiclient/discovery_cache/documents/gmail.v1.json
index f8669e1..4c6c492 100644
--- a/googleapiclient/discovery_cache/documents/gmail.v1.json
+++ b/googleapiclient/discovery_cache/documents/gmail.v1.json
@@ -384,7 +384,7 @@
                 },
                 "maxResults": {
                   "default": "100",
-                  "description": "Maximum number of drafts to return.",
+                  "description": "Maximum number of drafts to return. This field defaults to 100. The maximum allowed value for this field is 500.",
                   "format": "uint32",
                   "location": "query",
                   "type": "integer"
@@ -559,7 +559,7 @@
                 },
                 "maxResults": {
                   "default": "100",
-                  "description": "The maximum number of history records to return.",
+                  "description": "Maximum number of history records to return. This field defaults to 100. The maximum allowed value for this field is 500.",
                   "format": "uint32",
                   "location": "query",
                   "type": "integer"
@@ -1113,7 +1113,7 @@
                 },
                 "maxResults": {
                   "default": "100",
-                  "description": "Maximum number of messages to return.",
+                  "description": "Maximum number of messages to return. This field defaults to 100. The maximum allowed value for this field is 500.",
                   "format": "uint32",
                   "location": "query",
                   "type": "integer"
@@ -2541,7 +2541,7 @@
                 },
                 "maxResults": {
                   "default": "100",
-                  "description": "Maximum number of threads to return.",
+                  "description": "Maximum number of threads to return. This field defaults to 100. The maximum allowed value for this field is 500.",
                   "format": "uint32",
                   "location": "query",
                   "type": "integer"
@@ -2682,7 +2682,7 @@
       }
     }
   },
-  "revision": "20210607",
+  "revision": "20210614",
   "rootUrl": "https://gmail.googleapis.com/",
   "schemas": {
     "AutoForwarding": {