Require ros2_controllers version 2.12.0 in repos file

Since ros2_controllers broke its API in 2.13.0 and we reverted the API change
on this branch, we should let the CI know of that change.

Author: Felix Exner

Universal_Robots_ROS2_Driver.humble.repos

@@ -14,7 +14,7 @@ repositories:
   ros2_controllers:
     type: git
     url: https://github.com/ros-controls/ros2_controllers
-    version: master
+    version: 2.12.0
   kinematics_interface:
     type: git
     url: https://github.com/ros-controls/kinematics_interface.git