message: backend: fix warning
  variable ARBITRARY_CAMERA_STORAGE_STATUS was unused
diff: @@ -771,8 +771,8 @@ dronecode_sdk::Camera::CaptureInfo CameraServiceImplTest::createArbitraryCapture
  TEST_F(CameraServiceImplTest, registersToCameraStatus)
  {
  - const auto expected_camera_status = createCameraStatus(
  - false, true, dronecode_sdk::Camera::Status::StorageStatus::FORMATTED, 3.4f, 12.6f, 16.0f);
  + const auto expected_camera_status =
  + createCameraStatus(false, true, ARBITRARY_CAMERA_STORAGE_STATUS, 3.4f, 12.6f, 16.0f);
  dronecode_sdk::Camera::subscribe_status_callback_t status_callback;
  EXPECT_CALL(_camera, subscribe_status(_))
  .WillOnce(SaveResult(&status_callback, &_callback_saved_promise));
  @@ -838,8 +838,8 @@ TEST_F(CameraServiceImplTest, doesNotSendCameraStatusIfCallbackNotCalled)
  TEST_F(CameraServiceImplTest, sendsOneCameraStatus)
  {
  std::vector<dronecode_sdk::Camera::Status> camera_status_events;
  - auto camera_status_event = createCameraStatus(
  - false, true, dronecode_sdk::Camera::Status::StorageStatus::FORMATTED, 3.4f, 12.6f, 16.0f);
  + auto camera_status_event =
  + createCameraStatus(false, true, ARBITRARY_CAMERA_STORAGE_STATUS, 3.4f, 12.6f, 16.0f);
  camera_status_events.push_back(camera_status_event);
  checkSendsCameraStatus(camera_status_events);
  @@ -863,8 +863,8 @@ void CameraServiceImplTest::checkSendsCameraStatus(
  camera_status_callback(camera_status_event);
  }
  context->TryCancel();
  - auto arbitrary_camera_status_event = createCameraStatus(
  - false, true, dronecode_sdk::Camera::Status::StorageStatus::FORMATTED, 3.4f, 12.6f, 16.0f);
  + auto arbitrary_camera_status_event =
  + createCameraStatus(false, true, ARBITRARY_CAMERA_STORAGE_STATUS, 3.4f, 12.6f, 16.0f);
  camera_status_callback(arbitrary_camera_status_event);
  camera_status_events_future.wait();
  