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] <[email protected]>

pyproject.toml

@@ -67,7 +67,7 @@ docs = [
     'sphinx-copybutton~=0.5.2',
     'sphinx-markdown-tables~=0.0.17',
     'sphinx-rtd-theme~=2.0.0',
-    'sphinx~=8.0.2',
+    'sphinx~=8.1.3',
 ]
 lint = [
     'ruff~=0.6.3',