Bump sphinx from 5.1.0 to 5.1.1 in /docs (psf#3201)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 5.1.0 to 5.1.1.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/5.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v5.1.0...v5.1.1)

---
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

@@ -1,7 +1,7 @@
 # Used by ReadTheDocs; pinned requirements for stability.
 
 myst-parser==0.18.0
-Sphinx==5.1.0
+Sphinx==5.1.1
 # Older versions break Sphinx even though they're declared to be supported.
 docutils==0.18.1
 sphinxcontrib-programoutput==0.17