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] <support@github.com>

doc/requirements.txt

@@ -1,4 +1,4 @@
-Sphinx==5.3.0
+Sphinx==6.0.0
 sphinx-reredirects<1
 myst-parser~=0.18
 towncrier~=22.12