Bump sphinx from 4.3.2 to 4.4.0 in /docs

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 4.3.2 to 4.4.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/4.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v4.3.2...v4.4.0)

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

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

docs/requirements.txt

@@ -1,6 +1,6 @@
 # Used by ReadTheDocs; pinned requirements for stability.
 
 myst-parser==0.16.1
-Sphinx==4.3.2
+Sphinx==4.4.0
 sphinxcontrib-programoutput==0.17
 sphinx_copybutton==0.4.0