Set heartbeat autopilot correctly

According to the documentation, components that are
not autopilots, should set the heartbeat autopilot field
to MAV_AUTOPILOT_INVALID.
https://mavlink.io/en/services/heartbeat.html#component-identity

Signed-off-by: Soren Friis <soren.friis@intel.com>

RemoteIDModule/mavlink.cpp

@@ -62,7 +62,7 @@ void MAVLinkSerial::update_send(void)
         mavlink_msg_heartbeat_send(
             chan,
             MAV_TYPE_ODID,
-            MAV_AUTOPILOT_ARDUPILOTMEGA,
+            MAV_AUTOPILOT_INVALID,
             0,
             0,
             0);