Add simulation_gz repo to repos file

Author: fmauch

rolling.repos

@@ -11,6 +11,10 @@ repositories:
     type: git
     url: https://github.com/UniversalRobots/Universal_Robots_ROS2_Driver.git
     version: main
+  ur_simulation_gz:
+    type: git
+    url: https://github.com/UniversalRobots/Universal_Robots_ROS2_GZ_Simulation.git
+    version: ros2
   ur_tutorials:
     type: git
     url: https://github.com/UniversalRobots/Universal_Robots_ROS2_Tutorials.git