Removes deprecated ResultSet.subtasks (use ResultSet.results)

celery/result.py

@@ -726,11 +726,6 @@ class ResultSet(ResultBase):
         return '<{0}: [{1}]>'.format(type(self).__name__,
                                      ', '.join(r.id for r in self.results))
 
-    @property
-    def subtasks(self):
-        """Deprecated alias to :attr:`results`."""
-        return self.results
-
     @property
     def supports_native_join(self):
         try: