ci: remove mypy ignore imports for matplotlib

[SiQube]

needs #563 or #561

[codecov[bot]]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (99d7c31) 100.00% compared to head (4f1fc99) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #565 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 51 51 Lines 2234 2234 Branches 552 552 ========================================= Hits 2234 2234 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[SiQube]

okay how about we just kill mypy within github actions -- we're checking it via pre-commit.ci anyways. matplotlib 3.8 has dropped python 3.8... otherwise I'd say we stay at 3.7.3 with the already merged fix

[dkrako]

matplotlib 3.8 has dropped python 3.8... otherwise I'd say we stay at 3.7.3 with the already merged fix

The current numpy release is also python >=3.9: https://numpy.org/neps/nep-0029-deprecation_policy.html

I'm actually not that hesitant about dropping python 3.8 altogether (but then in a separate PR).

[SiQube]

requires #572

[SiQube]

fails due to polars not building wheels for windows, see here, and here.

[ritchie46]

fails due to polars not building wheels for windows, see here, and here.

Should be fixed now.