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/master/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

@@ -21,7 +21,7 @@ requests~=2.32.3
 six~=1.16.0
 snowballstemmer~=2.2.0
 soupsieve~=2.6
-Sphinx~=8.0.2
+Sphinx~=8.1.3
 sphinx-material~=0.0.36
 sphinxcontrib-applehelp~=2.0.0
 sphinxcontrib-devhelp~=2.0.0