Update Docker and README files

[jhanca-robotecai]

What does this PR do?

Minor fixes prior to release with 2409.2 engine:

• set 2409.2 tag for the engine and extras instead of the main branch in docker to ensure it builds correctly (it will not build with newer engine at this stage)
• remove patch that was used in one of the old engines
• update the documentation to use correct ROS 2 spelling (and ROS2 name of the gem)

How was this PR tested?

The docker was built and run:

cd docker ; docker build -t roscon_demo -f Dockerfile . ; 
docker run -it --rm \
  --gpus all \
  --network=bridge \
  -e DISPLAY=$DISPLAY \
  -v /tmp/.X11-unix:/tmp/.X11-unix \
  roscon_demo