Use ros2-testing debs for rolling (#308)

Author: esteve

.github/workflows/rust.yml

@@ -48,6 +48,7 @@ jobs:
       uses: ros-tooling/[email protected]
       with:
         required-ros-distributions: ${{ matrix.ros_distribution }}
+        use-ros2-testing: ${{ matrix.ros_distribution == 'rolling' }}
 
     - name: Downgrade pydocstyle as a workaround for https://github.com/ament/ament_lint/issues/434
       run: |