build(deps): update sphinx requirement in /requirements

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/v7.4.7/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v5.0.1...v7.4.7)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-version: 7.4.7
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements/docs.txt

@@ -1,4 +1,4 @@
-sphinx >5.0, <6.0
+sphinx >5.0, <8.0
 myst-parser >=0.18.1, <4.0.0
 nbsphinx >=0.8.5, <=0.9.7
 nbconvert >7.14, <7.17