Update sphinx requirement from <8,>=3.1 to >=3.1,<9 in /requirements (#…

…306)

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@v3.1.0...v8.0.2)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Denis Rouzaud <[email protected]>

requirements/documentation.txt

@@ -3,7 +3,7 @@
 
 furo==2024.*
 myst-parser[linkify]>=0.13,<3.1
-sphinx>=3.1,<8
+sphinx>=3.1,<9
 sphinx-autobuild==2024.9.19
 sphinx-copybutton>=0.2,<1
 sphinx-design>=0.6.0,<0.7