Bump sphinx from 7.3.7 to 8.1.3

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 7.3.7 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@v7.3.7...v8.1.3)

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

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

pyproject.toml

@@ -43,7 +43,7 @@ dev = [
     "wheel==0.43.0",
 ]
 docs = [
-    "sphinx==7.3.7",
+    "sphinx==8.1.3",
     "sphinx-mdinclude==0.6.2",
 ]