notes_for_developers.rst: Mention protoc limitation with relative import paths and workaround
Before raising this MR, consider whether the following are required, and complete if so:
- Unit tests
- Documentation update(s)
If not required, please explain in brief why not.
This adds a mention of the need to manually adjust import paths when generating protobufs to be used by BuildGrid.
Changes proposed in this merge request:
- Add a note in
docs/source/developer/notes_for_developers.rstabout having to adjust the modules generated by protobuf in order to make them relative to