FAQ: clarify 5.13 How do I stop an ongoing transfer

Rich Gray provided good feedback and we now clarify that you can in fact
stop a multi transfer at any point you like by removing the easy handle.

docs/FAQ

@@ -1287,7 +1287,7 @@ FAQ
 
   If you're using the multi interface, you can also stop a transfer by
   removing the particular easy handle from the multi stack at any moment you
-  think the transfer is done.
+  think the transfer is done or when you wish to abort the transfer.
 
   5.14 Using C++ non-static functions for callbacks?