Mypy error in asset golden files when adding dependency for google-cloud-org-policy

[parthea]

The dependency google-cloud-org-policy is needed in the generated client for //google/cloud/asset/v1. See https://github.com/googleapis/python-asset/blob/7c1f5fec48364889da95d21042278a9d944688c4/setup.py#L42

In PR #1805, when the GAPIC dependency google-cloud-org-policy was added, mypy tests fail with error Variable "google.cloud.orgpolicy.v1.orgpolicy_pb2.Policy" is not valid as a type .

See the build log here and stack trace below

nox > Running session mypy-3.11
nox > Creating virtual environment (virtualenv) using python3.11 in .nox/mypy-3-11
nox > python -m pip install mypy types-requests types-protobuf
nox > python -m pip install .
nox > mypy --explicit-package-bases google
google/cloud/asset_v1/types/assets.py:266: error: Variable "google.cloud.orgpolicy.v1.orgpolicy_pb2.Policy" is not valid as a type  [valid-type]
google/cloud/asset_v1/types/assets.py:266: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#variables-vs-type-aliases
Found 1 error in 1 file (checked 17 source files)

We don't currently have type stubs for google-cloud-org-policy so adding it would be a good starting point. Missing type stubs are missing in several core dependencies. Also see issue in googleapis/python-api-common-protos#135 for missing type stubs in googleapis-common-protos.