Python 2.7 no longer available in GitHub Actions by default

[dbieber]

Python 2.7 no longer available in GitHub Actions by default

This is causing our GitHub Actions to fail.

The error is:
Error: The version '2.7' with architecture 'x64' was not found for Ubuntu 20.04.

Options to resolve are: simply don't test with Python 2.7, or (preferred) find a different want to load 2.7 in GH Actions.
OK to take the former route first to get to a stable state faster, and to add 2.7 back in a follow up.

[dbieber]

See actions/setup-python#672 (comment)