Remove protobuf-compiler, protobuf-cpp, and protobuf-btr auto assign since they are too broad of a group. Prefer onduty to review or assign a reviewer. We keep auto assign for languages with small codebases and small support teams.

Remove protobuf-compiler, protobuf-cpp, and protobuf-btr auto assign since they are too broad of a group. Prefer onduty to review or assign a reviewer. We keep auto assign for languages with small codebases and small support teams. #70405