Bump sphinx from 4.3.2 to 6.1.1

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 4.3.2 to 6.1.1.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/v6.1.1/CHANGES)
- [Commits](sphinx-doc/sphinx@v4.3.2...v6.1.1)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

requirements_dev.txt

@@ -9,7 +9,7 @@ pip
 pytest-runner==5.3.1
 pytest==7.0.1
 recommonmark==0.7.1
-Sphinx==4.3.2
+Sphinx==6.1.1; python_version > '3.8'
 twine==3.8.0
 types-Jinja2==2.11.9
 types-pkg_resources==0.1.3