Build(deps): Bump sphinx from 4.1.2 to 4.2.0 in /docs (#467)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 4.1.2 to 4.2.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/4.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v4.1.2...v4.2.0)

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

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

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

docs/requirements.txt

@@ -1,2 +1,2 @@
-sphinx==4.1.2
+sphinx==4.2.0
 furo==2021.9.8