Address review: snapshot with list(); drop the NEWS entry

The fix is for an unrealized feature, so no NEWS is needed.

Author: tonghuaroot

Lib/multiprocessing/pool.py

@@ -668,7 +668,7 @@ def close(self):
             self._change_notifier.put(None)
             # Wake any task generator throttled on a buffersize semaphore so
             # it observes the CLOSE state and stops submitting.
-            for sema in tuple(self._taskqueue_buffersize_semaphores):
+            for sema in list(self._taskqueue_buffersize_semaphores):
                 sema.release()
 
     def terminate(self):