Improve pre-commit configuration

[DimitriPapadopoulos]

• Python 3 is the default nowadays, no need to specify it.
• Update pre-commmit less often that the "weekly" default.

TODO:

• Unit tests and/or doctests in docstrings
• Tests pass locally
• Docstrings and API docs for any new/modified user-facing classes and functions
• Changes documented in docs/release.rst
• Docs build locally
• GitHub Actions CI passes
• Test coverage to 100% (Codecov passes)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.92%. Comparing base (4b95d66) to head (8a9a0eb).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #668   +/-   ##
=======================================
  Coverage   99.92%   99.92%           
=======================================
  Files          62       62           
  Lines        2761     2761           
=======================================
  Hits         2759     2759           
  Misses          2        2