Fix duplicate rviz node names (moveit#672)

Remapping node names in ROS2 enforces this name for all (sub)nodes created in a process:
ros2/rclcpp#843

Author: Juliaj

demo/launch/demo.launch.py

@@ -37,7 +37,6 @@ def generate_launch_description():
     rviz_node = Node(
         package="rviz2",
         executable="rviz2",
-        name="rviz2",
         output="log",
         arguments=["-d", rviz_config_file],
         parameters=[