Use new default credentials in a few more modules

Updated Reporting (Beam pipeline), Registrar sync to sheets, and Cloud Dns.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=212811185

java/google/registry/config/CredentialModule.java

@@ -55,7 +55,12 @@ public abstract class CredentialModule {
     return credential;
   }
 
-  /** Provides a {@link GoogleCredential} from the service account's JSON key file. */
+  /**
+   * Provides a {@link GoogleCredential} from the service account's JSON key file.
+   *
+   * <p>On App Engine, a thread created using Java's built-in API needs this credential when it
+   * calls App Engine API. The Google Sheets API also needs this credential.
+   */
   @JsonCredential
   @Provides
   @Singleton

java/google/registry/config/files/default-config.yaml

@@ -188,7 +188,7 @@ credentialOAuth:
   defaultCredentialOauthScopes:
     # View and manage data in all Google Cloud APIs.
     - https://www.googleapis.com/auth/cloud-platform
-    # View and manage files in Google Drive.
+    # View and manage files in Google Drive, e.g., Docs and Sheets.
     - https://www.googleapis.com/auth/drive
   # OAuth scopes required for delegated admin access to G Suite domain.
   # Deployment of changes to this list must be coordinated with G Suite admin