fix: Allow protobuf 6.x

[parthea]

Apply changes from googleapis/gapic-generator-python#2352 and googleapis/gapic-generator-python#2347 to 4 packages containing protobuf stubs which are not automatically generated using gapic-generator-python

BEGIN_COMMIT_OVERRIDE
fix: Allow protobuf 6.x
fix: resolve issue where pre-release versions of dependencies are installed
END_COMMIT_OVERRIDE

[parthea]

presubmit core_deps_from_source failed https://github.com/googleapis/google-cloud-python/actions/runs/13775554603/job/38523909038

~/work/google-cloud-python/google-cloud-python/packages/google-cloud-access-context-manager ~/work/google-cloud-python/google-cloud-python
nox > Error while collecting sessions.
nox > Sessions not found: core_deps_from_source

This was fixed by 346097d

[vchudnov-g]

Thanks for doing this! One non-trivial (but still minor) comment about avoiding the try/catch.