Move TypeGuard import to the correct location in user_defined.py

Author: kosiew

python/datafusion/user_defined.py

@@ -28,12 +28,13 @@
     Callable,
     Optional,
     Protocol,
-    TypeGuard,
     TypeVar,
     cast,
     overload,
 )
 
+from typing_extensions import TypeGuard
+
 import pyarrow as pa
 
 import datafusion._internal as df_internal