build(deps): bump sphinx from 8.2.3 to 9.1.0 in /docs (#643)

Bumps [sphinx](https://github.com/sphinx-doc/sphinx) from 8.2.3 to 9.1.0.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v8.2.3...v9.1.0)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-version: 9.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

docs/pyproject.toml

@@ -18,7 +18,7 @@ dependencies = [
     "myst-parser==5.0.0",
     "rstcheck[sphinx]==6.2.5",
     "rstfmt==0.0.14",
-    "Sphinx==8.2.3",
+    "Sphinx==9.1.0",
     "sphinx-copybutton==0.5.2",
 ]