chore: Update discovery artifacts (#1336)

## Deleted keys were detected in the following stable discovery artifacts:
servicemanagementv1[ [More details]](https://github.com/googleapis/google-api-python-client/commit/6e593517543990b40c8c6a4c2512e176a0b896f4)

## Discovery Artifact Change Summary:
contentv21[ [More details]](https://github.com/googleapis/google-api-python-client/commit/e18a707b3351372b6bad9961a3cc0a1087fb907b)
dnsv1beta2[ [More details]](https://github.com/googleapis/google-api-python-client/commit/bb15dc54f5f110036bdb96d247d20f6908324547)
servicemanagementv1[ [More details]](https://github.com/googleapis/google-api-python-client/commit/6e593517543990b40c8c6a4c2512e176a0b896f4)
translatev3beta1[ [More details]](https://github.com/googleapis/google-api-python-client/commit/0ab9156b06cbc33b173851b20ab73bdd06522fe8)

chore(acceleratedmobilepageurl): update the api
chore(accessapproval): update the api
chore(adexchangebuyer): update the api
chore(adexchangebuyer2): update the api
chore(admob): update the api
chore(analyticsadmin): update the api
chore(analyticsdata): update the api
chore(analyticsreporting): update the api
chore(androiddeviceprovisioning): update the api
chore(androidmanagement): update the api
chore(apigateway): update the api
chore(apikeys): update the api
chore(area120tables): update the api
chore(calendar): update the api
chore(chromemanagement): update the api
chore(chromepolicy): update the api
chore(cloudchannel): update the api
chore(cloudkms): update the api
chore(cloudtasks): update the api
chore(composer): update the api
feat(content): update the api
chore(customsearch): update the api
chore(datastore): update the api
chore(dialogflow): update the api
chore(digitalassetlinks): update the api
feat(dns): update the api
chore(docs): update the api
chore(domainsrdap): update the api
chore(essentialcontacts): update the api
chore(eventarc): update the api
chore(factchecktools): update the api
chore(file): update the api
chore(firebase): update the api
chore(firebasedatabase): update the api
chore(firestore): update the api
chore(gmailpostmastertools): update the api
chore(indexing): update the api
chore(jobs): update the api
chore(libraryagent): update the api
chore(licensing): update the api
chore(manufacturers): update the api
chore(mybusinessaccountmanagement): update the api
chore(mybusinesslodging): update the api
chore(mybusinessplaceactions): update the api
chore(orgpolicy): update the api
chore(pagespeedonline): update the api
chore(paymentsresellersubscription): update the api
chore(policytroubleshooter): update the api
chore(prod_tt_sasportal): update the api
chore(realtimebidding): update the api
chore(runtimeconfig): update the api
chore(safebrowsing): update the api
chore(script): update the api
chore(serviceconsumermanagement): update the api
feat(servicemanagement): update the api
chore(serviceusage): update the api
chore(slides): update the api
chore(storage): update the api
chore(streetviewpublish): update the api
chore(tasks): update the api
chore(toolresults): update the api
feat(translate): update the api
chore(workflows): update the api
chore(youtube): update the api
chore(youtubeAnalytics): update the api
chore(youtubereporting): update the api
chore(docs): Add new discovery artifacts and reference documents
diff --git a/googleapiclient/discovery_cache/documents/serviceusage.v1.json b/googleapiclient/discovery_cache/documents/serviceusage.v1.json
index c892e55..8bb0992 100644
--- a/googleapiclient/discovery_cache/documents/serviceusage.v1.json
+++ b/googleapiclient/discovery_cache/documents/serviceusage.v1.json
@@ -426,7 +426,7 @@
       }
     }
   },
-  "revision": "20210428",
+  "revision": "20210501",
   "rootUrl": "https://serviceusage.googleapis.com/",
   "schemas": {
     "AdminQuotaPolicy": {
@@ -1054,7 +1054,7 @@
       "type": "object"
     },
     "Endpoint": {
-      "description": "`Endpoint` describes a network endpoint of a service that serves a set of APIs. It is commonly known as a service endpoint. A service may expose any number of service endpoints, and all service endpoints share the same service definition, such as quota limits and monitoring metrics. Example service configuration: name: library-example.googleapis.com endpoints: # Below entry makes 'google.example.library.v1.Library' # API be served from endpoint address library-example.googleapis.com. # It also allows HTTP OPTIONS calls to be passed to the backend, for # it to decide whether the subsequent cross-origin request is # allowed to proceed. - name: library-example.googleapis.com allow_cors: true",
+      "description": "`Endpoint` describes a network address of a service that serves a set of APIs. It is commonly known as a service endpoint. A service may expose any number of service endpoints, and all service endpoints share the same service definition, such as quota limits and monitoring metrics. Example: type: google.api.Service name: library-example.googleapis.com endpoints: # Declares network address `https://library-example.googleapis.com` # for service `library-example.googleapis.com`. The `https` scheme # is implicit for all service endpoints. Other schemes may be # supported in the future. - name: library-example.googleapis.com allow_cors: false - name: content-staging-library-example.googleapis.com # Allows HTTP OPTIONS calls to be passed to the API frontend, for it # to decide whether the subsequent cross-origin request is allowed # to proceed. allow_cors: true",
       "id": "Endpoint",
       "properties": {
         "allowCors": {