Update CI

[glatterf42]

Closes #788. This PR updates the CI to address several minor issues:

• Bump cache-action version
• Bump Codecov-action version using newly added repo secret
• Remove temporary genno pin

We can also use this to solve the current CI failure of the windows-tutorials test. As far as I can see, this failure stems from a cache being used -- at least, the setup-gams step does not fail for the other windows-CI-tests not using a cache for gams. (was resolved by iiasa/actions#12)

How to review

• Read the diff and note that the CI checks all pass.

PR checklist

• [x] Continuous integration checks all ✅
• [x] Add or expand tests; coverage checks both ✅
• ~[ ] Add, expand, or update documentation.~ Just CI updates
• ~[ ] Update release notes.~ Just CI updates

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (4dae41e) 95.2% compared to head (b26151a) 95.2%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #790 +/- ## ===================================== Coverage 95.2% 95.2% ===================================== Files 46 46 Lines 4335 4335 ===================================== Hits 4130 4130 Misses 205 205 ```

[glatterf42]

@khaeru This PR is ready in principle, the only thing we might want to still adapt is the pre-commit action usage.

[glatterf42]

Good catch, thanks :)