Sub: move sending of optical flow status up to base class

ArduSub/GCS_Mavlink.cpp

@@ -441,13 +441,6 @@ bool GCS_MAVLINK_Sub::try_send_message(enum ap_message id)
 #endif
         break;
 
-    case MSG_OPTICAL_FLOW:
-#if OPTFLOW == ENABLED
-        CHECK_PAYLOAD_SIZE(OPTICAL_FLOW);
-        send_opticalflow(sub.optflow);
-#endif
-        break;
-
     case MSG_PID_TUNING:
         CHECK_PAYLOAD_SIZE(PID_TUNING);
         sub.send_pid_tuning(chan);