Bump sphinx from 5.3.0 to 6.0.0

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 5.3.0 to 6.0.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES)
- [Commits](sphinx-doc/sphinx@v5.3.0...v6.0.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements/requirements_docs.txt

@@ -2,7 +2,7 @@ pypandoc==1.10
 imageio==2.22.2
 numpydoc==1.4.0
 imageio-ffmpeg==0.4.7
-Sphinx==5.3.0
+Sphinx==6.0.0
 sphinx-autobuild==2021.3.14
 sphinxcontrib-napoleon==0.7
 sphinxcontrib-websupport==1.2.4