MNT: Undo numpydoc pin when we can #10529

This is a follow-up of #10524 . When a new version of something (numpydoc, Sphinx, automodapi, etc) comes out upstream that fixes the :py:class reference target not found: warnings, we should remove this pinning:

If even then, some fix to our own docstrings is still needed, that fix should be applied as well.