chore(deps): Bump sphinx from 8.1.3 to 9.1.0

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 8.1.3 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](https://github.com/sphinx-doc/sphinx/compare/v8.1.3...v9.1.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -17,7 +17,7 @@ requests==2.32.5
 rst2pdf==0.104
 smartypants==2.0.2
 snowballstemmer==3.0.1
-Sphinx==8.1.3
+Sphinx==9.1.0
 sphinx-copybutton==0.5.2
 sphinx-rtd-theme==3.1.0
 sphinx-rtd-dark-mode==1.3.0