Update intersphinx_mapping for Sphinx 8 compatibility (#598)

[musicinmybrain]

This makes the intersphinx_mapping in docs/conf.py forward-compatible with Spinx 8 by changing it from

intersphinx_mapping = {"https://docs.python.org/3/": None}

to

intersphinx_mapping = {"python": ("https://docs.python.org/3/", None)}

• fixes The intersphinx_mapping in docs/conf.py is incompatible with Sphinx 8 #598

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change. N/A; test by building and inspecting the documentation
• Add or update relevant docs, in the docs folder and in code. N/A; nothing to document
• Add an entry in CHANGES.rst summarizing the change and linking to the issue.
• Add .. versionchanged:: entries in any relevant code docs. N/A; no code changes
• Run pre-commit hooks and fix any issues.
• Run pytest and tox, no tests failed.