message: core: remove duplicate registration
diff: @@ -12,13 +12,6 @@ MavlinkRequestMessageHandler::MavlinkRequestMessageHandler(SystemImpl& system_im
  return handle_command_long(command);
  },
  this);
  -
  - _system_impl.register_mavlink_command_handler(
  - MAV_CMD_REQUEST_MESSAGE,
  - [this](const MavlinkCommandReceiver::CommandLong& command) {
  - return handle_command_long(command);
  - },
  - this);
  }
  MavlinkRequestMessageHandler::~MavlinkRequestMessageHandler()
  