chore(deps): update sphinx requirement from <8,>=7.2.6 to >=7.2.6,<9

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/v8.0.2/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v7.2.6...v8.0.2)

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

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

docs/requirements.txt

@@ -1,4 +1,4 @@
 m2r2>=0.3.2
-sphinx>=7.2.6,<8
+sphinx>=7.2.6,<9
 sphinx-autoapi>=3.0.0,<4
 sphinx-rtd-theme>=2.0.0,<3