Use PEP 570 syntax in stdlib (#11250)

stdlib/pstats.pyi

@@ -48,7 +48,8 @@ class Stats:
     sort_arg_dict_default: _SortArgDict
     def __init__(
         self,
-        __arg: None | str | Profile | _cProfile = ...,
+        arg: None | str | Profile | _cProfile = ...,
+        /,
         *args: None | str | Profile | _cProfile | Self,
         stream: IO[Any] | None = None,
     ) -> None: ...