Google-api-python-client-stubs

- Regenerate stubs based on v2.1.0
- Add the missing `static_discovery` argument that was added to `build` in v2
- Fix the Python version constraint, Python 2 is no longer supported as of v2

This release adds support for v2 of google-api-python-client. The major change is that v2 bundles the discovery documents. The stubs are thus now based on the bundled documents and not the live ones. Note that because the bundled and live documents don't overlap completely, a few APIs no longer have stubs.

- Regenerate stubs
- Fix an issue with cyclic definitions in stubs
- Type the return value of `Resource.__enter__` so that type inference works when using a service as a context manager