Bump sphinx from 5.0.2 to 5.1.0 in /docs

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 5.0.2 to 5.1.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/5.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v5.0.2...v5.1.0)

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

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

Author: dependabot[bot]

docs/requirements.txt

@@ -1,2 +1,2 @@
 furo==2022.6.21
-sphinx==5.0.2
+sphinx==5.1.0