Update camera.cpp for compatibility with cv_bridge in ros2

[Maelic]

The lib won't compile with the latest version of ros2 vision_opencv in humble, source from this fix:

https://github.com/ros-planning/navigation2/issues/3455#issuecomment-1459616739

[victorpaleologue]

Thanks! I've put your change in one of my works, it's now on main.