Fix typos

[PhilMiller]

Result of running ispell over /*.rst and /docs/source/*.rst

[PhilMiller]

CI failure is due to an unrelated deprecation warning on the existing code:

WARNING: The pre-Sphinx 1.0 'intersphinx_mapping' format is deprecated and will be removed in Sphinx 8. Update to the current format as described in the documentation. Hint: "intersphinx_mapping = {'<name>': ('https://docs.python.org/', None)}".https://www.sphinx-doc.org/en/master/usage/extensions/intersphinx.html#confval-intersphinx_mapping

[mdpiper]

@PhilMiller If you merge branch stable into your feature branch, this warning is fixed.

[PhilMiller]

Do you want me to re-target this at stable, or to implicitly have a merge of stable into develop as part of my change?

If there's some written guidance on the preferred flow, I'm happy to take a link.