chore: udpate protobuf dependency to match workspace (#1670)

Author: alicejli

gax-java/dependencies.properties

@@ -23,7 +23,7 @@ version.gax_httpjson=0.111.1-SNAPSHOT
 # Versions for dependencies which actual artifacts differ between Bazel and Gradle.
 # Gradle build depends on prebuilt maven artifacts, while Bazel build depends on Bazel workspaces
 # with the sources.
-version.com_google_protobuf=3.21.10
+version.com_google_protobuf=3.21.12
 version.google_java_format=1.15.0
 version.io_grpc=1.54.0