Build(deps): Bump sphinx from 8.0.2 to 8.1.3 (#1818)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 8.0.2 to 8.1.3.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/v8.1.3/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v8.0.2...v8.1.3)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Cooper Lees <me@cooperlees.com>

requirements_docs.txt

@@ -4,7 +4,7 @@ python-dateutil==2.9.0.post0
 packaging==24.1
 requests==2.32.3
 six==1.16.0
-sphinx==8.0.2
+sphinx==8.1.3
 MyST-Parser==4.0.0
 xmlrpc2==0.3.1
 sphinx-argparse-cli==1.18.2