fix lint : extra space after 'Future'

Author: manoj-k-m

Lib/asyncio/futures.py

@@ -161,7 +161,7 @@ def cancel(self, msg=None):
         return True.
 
         The optional argument *msg* is passed as the argument to the
-        asyncio.CancelledError exception raised when a cancelled Future 
+        asyncio.CancelledError exception raised when a cancelled Future
         is awaited. It can be any object.
         """
         self.__log_traceback = False