mypy

8f51fbf4 - Fix confusion between stubs for google.protobuf and google.cloud (#10609)

Fix confusion between stubs for google.protobuf and google.cloud (#10609) Previously we used `google` as a package prefix for `google.protobuf`. That wasn't correct, since there are other packages in the Google namespace, such as `google.cloud`. This fixes the prefix to to be `google.protobuf`. Fixes #10601.