Move to Python 3.11

[timmens]

Make Python 3.11 the default version in the outer and inner projects.

I had to

• edit the GitHub actions workflow file, as Python 3.11 is downloaded from conda-forge
• remove conda-build and mypy from the environment files (which is no problem since we don't use it anymore)

I also removed other unused packages from the environment files.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (update-docs@5e74309). Click here to learn what that means.
The diff coverage is n/a.

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  Hits                   ?        55           
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Flag	Coverage Δ
end_to_end	100.00% <0.00%> (?)

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[hmgaudecker]

Thanks a ton!