chore: Update discovery artifacts (#1398)

## Deleted keys were detected in the following stable discovery artifacts:
displayvideo v1 https://github.com/googleapis/google-api-python-client/commit/f6b1a8e2d291c2ac9d2ea590101bb3c8c6fbe6cf

## Discovery Artifact Change Summary:
feat(displayvideo): update the api https://github.com/googleapis/google-api-python-client/commit/f6b1a8e2d291c2ac9d2ea590101bb3c8c6fbe6cf
diff --git a/googleapiclient/discovery_cache/documents/tagmanager.v2.json b/googleapiclient/discovery_cache/documents/tagmanager.v2.json
index c61e259..6dd144a 100644
--- a/googleapiclient/discovery_cache/documents/tagmanager.v2.json
+++ b/googleapiclient/discovery_cache/documents/tagmanager.v2.json
@@ -3125,7 +3125,7 @@
       }
     }
   },
-  "revision": "20210526",
+  "revision": "20210602",
   "rootUrl": "https://tagmanager.googleapis.com/",
   "schemas": {
     "Account": {
@@ -4970,6 +4970,9 @@
             "windowLoaded",
             "customEvent",
             "triggerGroup",
+            "init",
+            "consentInit",
+            "serverPageview",
             "always",
             "firebaseAppException",
             "firebaseAppUpdate",
@@ -5029,6 +5032,9 @@
             "",
             "",
             "",
+            "",
+            "",
+            "",
             ""
           ],
           "type": "string"