Update sphinx requirement in /docs

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](sphinx-doc/sphinx@v7.0.0...v9.0.1)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-version: 9.0.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

docs/requirements.txt

@@ -1,4 +1,4 @@
-sphinx >=7.0.0,<9.0.0
+sphinx >=7.0.0,<10.0.0
 furo
 myst-parser
 sphinxcontrib-googleanalytics