Add type annotation for multiprocessing.SimpleQueue.close() method (#5814)

stdlib/multiprocessing/queues.pyi

@@ -28,6 +28,8 @@ class JoinableQueue(Queue[_T]):
 
 class SimpleQueue(Generic[_T]):
     def __init__(self, *, ctx: Any = ...) -> None: ...
+    if sys.version_info >= (3, 9):
+        def close(self) -> None: ...
     def empty(self) -> bool: ...
     def get(self) -> _T: ...
     def put(self, item: _T) -> None: ...