Update dependency sphinx to v9

Author: renovate[bot]

pyproject.toml

@@ -28,7 +28,7 @@ dependencies = ["pyyaml", "requests", "py", "importlib_resources~=6.3"]
 
 [project.optional-dependencies]
 test = ["coverage", "pytest"]
-doc = ["Sphinx~=6.2", "sphinx_rtd_theme~=1.3"]
+doc = ["Sphinx~=9.1", "sphinx_rtd_theme~=1.3"]
 
 [project.urls]
 Homepage = "https://github.com/dials/data"