Remove distutils from setup.py
[distutils](https://docs.python.org/3/library/distutils.html) is on its
way out and will be deprecated-on-import for Python 3.10+ and removed in
Python 3.12 (see [PEP 632](https://www.python.org/dev/peps/pep-0632/)).
There's no reason for us to keep it around since all the functionality
we want from it can be found in `setuptools`.t s
