Bump sphinx from 4.3.0 to 4.3.1 in /docs (#713)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 4.3.0 to 4.3.1.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/4.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v4.3.0...v4.3.1)

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

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

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

docs/requirements.txt

@@ -1,3 +1,3 @@
 furo==2021.11.23
-sphinx==4.3.0
+sphinx==4.3.1
 sphinx-click==3.0.2