Patch methods should return AsyncMock if the target is an async method

[GDYendell]

This would match the behaviour of the equivalent methods in mock

Currently, I can pass new_callable=AsyncMock to make it work, but then mypy type checking fails because the type hints state that the methods return MagicMock. The return type is a union in the mock stubs.

[nicoddemus]

Hi @GDYendell, thanks for bringing this to attention.