CI: Explicit Python version #207

Job	Run time
Check formatting of pySplashsurf crate	7s
Build wheel for documentation and tests	3m 7s
Run stub generator	30s
Build source distribution	11s
Build wheels for macOS aarch64	2m 21s
Build wheels for Windows i686	6m 58s
Build wheels for Windows aarch64	4m 26s
Build wheels for Windows x86_64	5m 9s
Build wheels for Linux aarch64	3m 46s
Build wheels for Linux x86_64	3m 7s
Build wheels for Linux i686	5m 17s
Build wheels for Linux armv7	3m 26s
Run pytest	2m 17s
Build documentation	23s
Publish to PyPI	0s
Read the Docs trigger	0s
	41m 5s

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