Update sphinx requirement from >=8.2.3 to >=9.1.0 (#241)

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/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:development
...

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

Author: dependabot[bot]

pyproject.toml

@@ -71,7 +71,7 @@ changelog = [
 ]
 docs = [
     "pydata-sphinx-theme>=0.17.1",
-    "sphinx>=8.2.3",
+    "sphinx>=9.1.0",
     "sphinx-autoapi>=3.8.0",
     "sphinx-autodoc-typehints>=3.10.2",
     "sphinx-click>=6.0.0",