Plane: add comment about us sending airspeed error in wrong units

ArduPlane/GCS_Mavlink.cpp

@@ -184,7 +184,7 @@ void GCS_MAVLINK_Plane::send_nav_controller_output() const
             wp_nav_valid ? quadplane.wp_nav->get_wp_bearing_to_destination() : 0,
             wp_nav_valid ? MIN(quadplane.wp_nav->get_wp_distance_to_destination() * 0.01, UINT16_MAX) : 0,
             (plane.control_mode != &plane.mode_qstabilize) ? quadplane.pos_control->get_pos_error_z_cm() * 0.01 : 0,
-            plane.airspeed_error * 100,
+            plane.airspeed_error * 100,  // incorrect units; see PR#7933
             wp_nav_valid ? quadplane.wp_nav->crosstrack_error() : 0);
         return;
     }
@@ -199,7 +199,7 @@ void GCS_MAVLINK_Plane::send_nav_controller_output() const
             nav_controller->target_bearing_cd() * 0.01,
             MIN(plane.auto_state.wp_distance, UINT16_MAX),
             plane.altitude_error_cm * 0.01,
-            plane.airspeed_error * 100,
+            plane.airspeed_error * 100,  // incorrect units; see PR#7933
             nav_controller->crosstrack_error());
     }
 }