[gc] Add default values (#15253)

Author: donbarbos

stdlib/gc.pyi

@@ -30,4 +30,4 @@ def is_tracked(obj: Any, /) -> bool: ...
 def is_finalized(obj: Any, /) -> bool: ...
 def isenabled() -> bool: ...
 def set_debug(flags: int, /) -> None: ...
-def set_threshold(threshold0: int, threshold1: int = ..., threshold2: int = ..., /) -> None: ...
+def set_threshold(threshold0: int, threshold1: int = 0, threshold2: int = 0, /) -> None: ...