Update sphinx requirement from <9,>=8.1.3 to >=8.1.3,<10

Updates the requirements on [sphinx](https://github.com/sphinx-doc/sphinx) to permit the latest version.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES.rst)
- [Commits](https://github.com/sphinx-doc/sphinx/compare/v8.1.3...v9.0.0

)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-version: 9.0.0
  dependency-type: direct:development
...

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