stub_uploader: verify external stub packages require runtime

[srittau]

We currently have a check in stub_uploader that external stubs packages require their runtime package:

https://github.com/typeshed-internal/stub_uploader/blob/de903bfb39be09084b72ceee6854ecae40ef2db0/stub_uploader/metadata.py#L335

This breaks for the suggested pydbus stubs (#13921), which depend on PyGObject-stubs, but PyGObject-stubs doesn't depend on PyGObject:

https://github.com/python/typeshed/actions/runs/14886712852/job/41808156011?pr=13921#step:6:206

Does anyone remember or know why we have this check? And what should we do about it?

1. Remove the check, because it doesn't serve a known purpose?
2. Add an exception list to the check?
3. Remove the dependency on PyGObject-stubs from pydbus and use Any or stub protocols instead?

[hauntsaninja]

It's to try and avoid security issues: #5768 (comment)