Tweak Python versions in CI

[bfontaine]

• Drop CI support for 2.7 (https://github.com/actions/setup-python/issues/672)
• Pin Ubuntu to 20.04 to fix support for 3.6 (https://github.com/actions/setup-python/issues/544)
• Add Python recent versions: 3.11, 3.12

This should fix the build for https://github.com/swaroopch/edn_format/pull/89.

[bfontaine]

This seems to be stuck: it’s waiting for the build on 2.7, but I removed it so it will never run.

Edit: I opened this discussion about the issue.

[bfontaine]

I was thinking that we could keep the Python 2.7 support as a "best effort": remove it from the CI but keep the code for it, at least for now.

[swaroopch]

I was thinking that we could keep the Python 2.7 support as a "best effort": remove it from the CI but keep the code for it, at least for now.

I'm ok with that 👍🏽

[bfontaine]

@swaroopch I think this is stuck; the only way I see to fix this is to temporarily unprotect master, merge the PR, then protect it again.

[swaroopch]

Force merged, let me know if that helps.

[bfontaine]

Thanks!