Change requirement to Python 3.11

because of tomllib.

Author: rgaiacs

setup.py

@@ -62,7 +62,7 @@ def get_identifier(json):
         "toml",
         "traitlets",
     ],
-    python_requires=">=3.9",
+    python_requires=">=3.11",
     author="Project Jupyter Contributors",
     author_email="[email protected]",
     url="https://repo2docker.readthedocs.io/en/latest/",