Bump sphinx from 7.2.6 to 7.3.7 in /requirements

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 7.2.6 to 7.3.7.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v7.2.6...v7.3.7)

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

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

requirements/docs.txt

@@ -1,2 +1,2 @@
-Sphinx==7.2.6
+Sphinx==7.3.7
 sphinx-rtd-theme==1.3.0