py-virtualenv: updated to 20.16.6

v20.16.6 (2022-10-25)
---------------------

Features - 20.16.6
- Drop unneeded shims for PyPy3 directory structure

Bugfixes - 20.16.6
- Fix selected scheme on debian derivatives for python 3.10 when ``python3-distutils`` is not installed or the ``venv`` scheme is not avaiable
- Allow the test suite to pass even with the original C shell (rather than ``tcsh``)
- Fix fallback handling of downloading wheels for bundled packages
- Upgrade embedded setuptools to ``65.5.0`` from ``65.3.0`` and pip to ``22.3`` from ``22.2.2``

(adam)