Deprecation warning for getting MarkupSafe version

[ryanscovill]

The following deprecation warning is displayed with getting the version of MarkupSafe. The __version__ attribute will be removed in MarkupSafe 3.1.

pybrake/notifier.py:394: UserWarning: The '__version__' attribute is deprecated and will be removed in MarkupSafe 3.1. Use feature detection, or `importlib.metadata.version("markupsafe")`, instead.

    if hasattr(mod, "__version__"):

This was introduced in pallets/markupsafe#402

Workaround:
The temporary monkeypatch proposed in #269 (comment) will apply here as well.