chore: drop Python 3.9 (and syntax) (#6289)

* `strict=False` is the default, pyupgrade to min version 3.10 adds this
to be explicit w/ behavior

libs/cli/langgraph_cli/progress.py

@@ -1,7 +1,7 @@
 import sys
 import threading
 import time
-from typing import Callable
+from collections.abc import Callable
 
 
 class Progress: