Update sphinx requirement from ~=8.0.2 to ~=8.1.3

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/v8.1.3/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v8.0.2...v8.1.3)

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

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

requirements.txt

@@ -7,4 +7,4 @@ sphinx-notfound-page>=1.0.0
 sphinx_copybutton>=0.3.3
 sphinxext-opengraph>=0.7.1
 sphinxext-rediraffe
-Sphinx~=8.0.2
+Sphinx~=8.1.3