Fix typo mentioning threads instead of tasks (python#123203)

Lib/asyncio/locks.py

@@ -341,9 +341,9 @@ def _notify(self, n):
                 fut.set_result(False)
 
     def notify_all(self):
-        """Wake up all threads waiting on this condition. This method acts
-        like notify(), but wakes up all waiting threads instead of one. If the
-        calling thread has not acquired the lock when this method is called,
+        """Wake up all tasks waiting on this condition. This method acts
+        like notify(), but wakes up all waiting tasks instead of one. If the
+        calling task has not acquired the lock when this method is called,
         a RuntimeError is raised.
         """
         self.notify(len(self._waiters))