Fix variable interpolation in YAML workflow

Author: marc-hanheide

.github/workflows/copilot-setup-steps.yml

@@ -34,12 +34,12 @@ jobs:
       - name: install workspace dependencies
         run: |
           sudo apt-get update
-          sudo apt-get install -y ros-${ROS_DISTRO}-ros-base
-          source /opt/ros/${ROS_DISTRO}/setup.bash
-          rosdep update --rosdistro ${ROS_DISTRO}
+          sudo apt-get install -y ros-$ROS_DISTRO-ros-base
+          source /opt/ros/$ROS_DISTRO/setup.bash
+          rosdep update --rosdistro $ROS_DISTRO
           rosdep install --from-paths src --ignore-src -r -y
 
       - name: build workspace
         run: |
-          source /opt/ros/${ROS_DISTRO}/setup.bash
+          source /opt/ros/$ROS_DISTRO/setup.bash
           colcon build --symlink-install --continue-on-error