Use Final for undocumented constants (#12450)

stdlib/argparse.pyi

@@ -51,7 +51,7 @@ _SUPPRESS_T = NewType("_SUPPRESS_T", str)
 SUPPRESS: _SUPPRESS_T | str  # not using Literal because argparse sometimes compares SUPPRESS with is
 # the | str is there so that foo = argparse.SUPPRESS; foo = "test" checks out in mypy
 ZERO_OR_MORE: Final = "*"
-_UNRECOGNIZED_ARGS_ATTR: str  # undocumented
+_UNRECOGNIZED_ARGS_ATTR: Final[str]  # undocumented
 
 class ArgumentError(Exception):
     argument_name: str | None