Update run-tests.yml

[itziakos]

• Test on Python 3.11
• Test on macos
• Generate coverage artifact
• Fix flake8 errors (but do not touch the regexes)

[itziakos]

@dpinte ubuntu-latest and windows-latest do not support testing on Python 3.6. Can we update the required jobs?

[dpinte]

@dpinte ubuntu-latest and windows-latest do not support testing on Python 3.6. Can we update the required jobs?

+1. Can you do it?