remove is_reply

fixed_reply.py

@@ -48,5 +48,5 @@ class FixedReplyFlow(AtomicFlow):
             input_message=input_message,
             response={"fixed_reply": self.flow_config["fixed_reply"]}
         )
-        self.send_message(reply, is_reply = True)
+        self.send_message(reply)