[Forwardport Rolling] Fix incorrect subscription on demo (#405)

[ahcorde]

🦟 Bug fix

Summary

This PR fixes an incorrect subscription on one of the demos. Running

ros2 launch ros_gz_sim_demos gpu_lidar_bridge.launch.py

causes rviz2 to crash and exit with the error:

rviz2-3]
[rviz2-3] >>> [rcutils|error_handling.c:108] rcutils_set_error_state()
[rviz2-3] This error state is being overwritten:
[rviz2-3]
[rviz2-3]   'create_subscription() called for existing topic name rt/lidar with incompatible type sensor_msgs::msg::dds_::PointCloud2_, at ./src/subscription.cpp:146, at ./src/rcl/subscription.c:108'
[rviz2-3]
[rviz2-3] with this new error message:
[rviz2-3]
[rviz2-3]   'invalid allocator, at ./src/rcl/subscription.c:218'
[rviz2-3]
[rviz2-3] rcutils_reset_error() should be called after error handling to avoid this.

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• Consider updating Python bindings (if the library has them)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
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