Test on CI that update-meson is properly ran

[user202729]

Fixes #39172

Side note, can we just include the __init__.py to be tracked by git?

📝 Checklist

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• I have created tests covering the changes. (not applicable)
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[orlitzky]

Side note, can we just include the __init__.py to be tracked by git?

@tobiasdiez tried this once and it launched a months-long battle. It affects the sagemath-{objects,categories,etc} namespace packages. Though at this point they are unmaintained, nobody should be using them, and we could be more pragmatic about fixing whatever goes wrong.