[sys.monitoring] Change return type of set_local_events to None (#15216)

Author: guoci

stdlib/sys/_monitoring.pyi

@@ -59,7 +59,7 @@ class _events:
 def get_events(tool_id: int, /) -> int: ...
 def set_events(tool_id: int, event_set: int, /) -> None: ...
 def get_local_events(tool_id: int, code: CodeType, /) -> int: ...
-def set_local_events(tool_id: int, code: CodeType, event_set: int, /) -> int: ...
+def set_local_events(tool_id: int, code: CodeType, event_set: int, /) -> None: ...
 def restart_events() -> None: ...
 
 DISABLE: Final[object]