GCS_MAVLink: pass mavlink_command_ack_t to accelcal library

The library needs to look at the content of the packet.  Given that GCS_MAVLink is already within handle_command_ack, decoding it there makes sense.

libraries/GCS_MAVLink/GCS_Common.cpp

@@ -3356,9 +3356,12 @@ void GCS_MAVLINK::handle_vision_speed_estimate(const mavlink_message_t &msg)
 void GCS_MAVLINK::handle_command_ack(const mavlink_message_t &msg)
 {
 #if HAL_INS_ACCELCAL_ENABLED
+    mavlink_command_ack_t packet;
+    mavlink_msg_command_ack_decode(&msg, &packet);
+
     AP_AccelCal *accelcal = AP::ins().get_acal();
     if (accelcal != nullptr) {
-        accelcal->handleMessage(msg);
+        accelcal->handle_command_ack(packet);
     }
 #endif
 }