Bump sphinx from 9.0.4 to 9.1.0 (#571)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 9.0.4 to 9.1.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v9.0.4...v9.1.0)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-version: 9.1.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements/lint.txt

@@ -1,7 +1,7 @@
 -r ci.txt
 mypy==1.19.1; implementation_name=="cpython"
 pre-commit==4.5.1
-sphinx==9.0.4
+sphinx==9.1.0
 sphinxcontrib-asyncio==0.3.0
 sphinxcontrib-spelling==8.0.2
 towncrier==25.8.0