stdlib: add argument default values (#9501)

stdlib/copyreg.pyi

@@ -10,7 +10,7 @@ __all__ = ["pickle", "constructor", "add_extension", "remove_extension", "clear_
 def pickle(
     ob_type: type[_T],
     pickle_function: Callable[[_T], str | _Reduce[_T]],
-    constructor_ob: Callable[[_Reduce[_T]], _T] | None = ...,
+    constructor_ob: Callable[[_Reduce[_T]], _T] | None = None,
 ) -> None: ...
 def constructor(object: Callable[[_Reduce[_T]], _T]) -> None: ...
 def add_extension(module: Hashable, name: Hashable, code: SupportsInt) -> None: ...