Bump sphinx from 8.1.0 to 8.1.3

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 8.1.0 to 8.1.3.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v8.1.0...v8.1.3)

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

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

pyproject.toml

@@ -47,7 +47,7 @@ marshmallow = ["marshmallow>=3.18.0"]
 docs = [
   "apispec[marshmallow]",
   "pyyaml==6.0.2",
-  "sphinx==8.1.0",
+  "sphinx==8.1.3",
   "sphinx-issues==4.1.0",
   "sphinx-rtd-theme==3.0.1",
 ]