build: raise minimum required matplotlib version to 3.5.0

[alexander-held]

The figure layout refactor introduced in cabinetry 0.5.0 requires matplotlib 3.5.0 or newer. Raise the minimum required version accordingly to prevent crashes with older versions.

resolves #369

* raise minimum required matplotlib version to 3.5.0

[codecov[bot]]

Codecov Report

Base: 100.00% // Head: 100.00% // No change to project coverage :thumbsup:

Coverage data is based on head (207ec76) compared to base (564fef7). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #370 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 23 23 Lines 2023 2023 Branches 320 320 ========================================= Hits 2023 2023 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scikit-hep). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=scikit-hep)

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