Originally we had this running as part of the Unit Tests job because most
of the checks are relatively fast. However, the addition of the protobuf
generation check made that no longer be true because it needs to download
and run protoc.

With that extra overhead it now _is_ productive to spend the time booting
and installing Go on third worker, as long as GitHub Actions continues
to let us run all three of these jobs concurrently most of the time.