Update sphinx requirement in the python group across 1 directory

Updates the requirements on [sphinx](https://github.com/sphinx-doc/sphinx) to permit the latest version.

Updates `sphinx` to 9.0.4
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/v9.0.4/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v0.1.61611...v9.0.4)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-version: 9.0.4
  dependency-type: direct:production
  dependency-group: python
...

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

Author: dependabot[bot]

pyproject.toml

@@ -9,7 +9,7 @@ dependencies = [
     "pydantic>=2.12.4",
     "requests>=2.32.5",
     "sphinx-rtd-theme>=3.0.2",
-    "sphinx<9",  # see https://github.com/executablebooks/MyST-Parser/issues/1077
+    "sphinx<10",  # see https://github.com/executablebooks/MyST-Parser/issues/1077
     "sphinxemoji>=0.3.1",
 ]