Bump sphinx from 4.2.0 to 4.3.0

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 4.2.0 to 4.3.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/4.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v4.2.0...v4.3.0)

---
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

@@ -1,3 +1,3 @@
-sphinx==4.2.0
+sphinx==4.3.0
 sphinx_rtd_theme==1.0.0
 readthedocs-sphinx-search==0.1.1