build(deps): update sphinx requirement from ~=7.2.6 to ~=7.3.7

Updates the requirements on [sphinx](https://github.com/sphinx-doc/sphinx) to permit the latest version.
- [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
...

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

docs/requirements.txt

@@ -1,2 +1,2 @@
-sphinx~=7.2.6
+sphinx~=7.3.7
 sphinx-rtd-theme~=2.0.0