Add __slots__ to third-party packages using stubdefaulter (#14619)

stubs/psutil/psutil/_psosx.pyi

@@ -79,6 +79,7 @@ def is_zombie(pid): ...
 def wrap_exceptions(fun): ...
 
 class Process:
+    __slots__ = ["_cache", "_name", "_ppid", "pid"]
     pid: Any
     def __init__(self, pid) -> None: ...
     def oneshot_enter(self) -> None: ...