Step 5.2.1 Remove unnecessary namespace 'camera'.
Open configuration file
sudo vi /opt/ros/humble/share/realsense2_camera/launch/rs_launch.py
Delete default value 'camera' of the camera_namespace. That means line below change from
{'name': 'camera_namespace', 'default': 'camera', 'description': 'namespace for camera'}
to
{'name': 'camera_namespace', 'default': '', 'description': 'namespace for camera'}