Update sphinx requirement from <7.2 to <8.1

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/v8.0.2/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v0.1.61611...v8.0.2)

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

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

pyproject.toml

@@ -83,7 +83,7 @@ dynamic = [
   "version",
 ]
 dependencies = [
-  "sphinx<7.2",
+  "sphinx<8.1",
   "sphinx-design==0.6.1",
 ]
 [project.optional-dependencies]