Bump protobuf-java from 3.19.3 to 3.21.9 in /plugins/repository-gcs

Bumps [protobuf-java](https://github.com/protocolbuffers/protobuf) from 3.19.3 to 3.21.9.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/generate_changelog.py)
- [Commits](protocolbuffers/protobuf@v3.19.3...v3.21.9)

---
updated-dependencies:
- dependency-name: com.google.protobuf:protobuf-java
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

plugins/repository-gcs/build.gradle

@@ -66,7 +66,7 @@ dependencies {
   api 'com.google.api:gax:2.17.0'
   api 'org.threeten:threetenbp:1.4.4'
   api 'com.google.protobuf:protobuf-java-util:3.20.0'
-  api 'com.google.protobuf:protobuf-java:3.19.3'
+  api 'com.google.protobuf:protobuf-java:3.21.9'
   api 'com.google.code.gson:gson:2.9.0'
   api 'com.google.api.grpc:proto-google-common-protos:2.8.0'
   api 'com.google.api.grpc:proto-google-iam-v1:0.12.0'