Fix black pre-commit stage & align line lengths

Explanation of changes

PROTIP: To avoid conflicts, try running the following before rebasing/merging your MR:

• git cherry-pick 7e9748df670d073a33516d567f129e51cd47811b
• pre-commit run black --files <your staged files> (or --all-files)

I'm fixing both SE-621 and SE-622 with this, as two separates MRs would be a waste of time.

• Pre-commit stage for black is now pre-commit as it should.
• Line length for black is now configured in pyproject.toml as 100.
• I also took the liberty of tidying up the format of the file to my taste.

Motivation of changes

With our big monitors 100 characters are better than 88, aren't they?

We can have a vote. React to this description with 💯 for 100 and 🎱 for 88.

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Merge checklist

See also merge request guidelines

• Merge request has been reviewed (in-depth by a knowledgeable contributor), and is approved by a project maintainer.
• New code is covered by unit tests (or N/A).
• New code is documented and docstrings use numpydoc format (or N/A).
• New functionality: considered making private instead of extending public API (or N/A).
• Public API changed: added @deprecated and entry in deprecated code suggestions (or N/A).
• Newly added/adjusted documentation and docstrings render properly (or N/A).
• Pipeline fix or dependency update: post in #software-for-developers channel to merge main back in or update local packages (or N/A).
• Tested on hardware (or N/A).
• CHANGELOG.md for breaking changes and AUTHORS.md have been updated (or N/A).
• Update Hardware backends documentation if backend interface change or N/A
• Check whether performance is significantly affected by looking at the Performance metrics results.
• Windows tests in CI pipeline pass (manually triggered by maintainers before merging).
  • Maintainers do not hit Auto-merge, we need to actively check as manual tests do not block pipeline

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For reference, the issues workflow is described in the contribution guidelines.