fix(dev): pre-commit virtualenv 20.0.23 -> 20.0.32

[joshuarli]

Currently in a fresh py3 venv, when running make setup-git you'll get the nonfatal:

ERROR: After October 2020 you may experience errors when installing or updating packages. This is because pip will change the way that it resolves dependency conflicts.

We recommend you use --use-feature=2020-resolver to test your packages with the new resolver before it becomes the default.

virtualenv 20.0.23 requires importlib-metadata<2,>=0.12; python_version < "3.8", but you'll have importlib-metadata 2.0.0 which is incompatible.

This upgrades virtualenv (for pre-commit) to 20.0.32 which includes the fix: pypa/virtualenv#1953. pre-commit does not yet have an upper pin for virtualenv which caused problems in the past with virtualenv, see #19256.

Tested in provisioning a fresh venv in both py2 + py3.