Fix docstring typo in concurrent.futures.Future
diff --git a/Lib/concurrent/futures/_base.py b/Lib/concurrent/futures/_base.py
index 883d993..e9f6537 100644
--- a/Lib/concurrent/futures/_base.py
+++ b/Lib/concurrent/futures/_base.py
@@ -331,7 +331,7 @@
         return True
 
     def cancelled(self):
-        """Return True if the future has cancelled."""
+        """Return True if the future was cancelled."""
         with self._condition:
             return self._state in [CANCELLED, CANCELLED_AND_NOTIFIED]