Update typing_extensions imports in stdlib (#11244)

Co-authored-by: AlexWaygood <alex.waygood@gmail.com>

stdlib/keyword.pyi

@@ -1,6 +1,6 @@
 import sys
 from collections.abc import Sequence
-from typing_extensions import Final
+from typing import Final
 
 if sys.version_info >= (3, 9):
     __all__ = ["iskeyword", "issoftkeyword", "kwlist", "softkwlist"]