Run CI only on Iron

.github/workflows/ci.yml

@@ -19,15 +19,9 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          # Test supported ROS 2 distributions
-          # https://docs.ros.org/en/rolling/Releases.html
-          # NOTE: Humble does not work on the `ros2` branch, so it is tested in its own branch.
+          # NOTE: Tests only Iron since the `ros2` branch tests later distros.
           - ros: iron
             os: ubuntu-22.04
-          - ros: jazzy
-            os: ubuntu-24.04
-          - ros: rolling
-            os: ubuntu-24.04
 
     name: ROS 2 ${{ matrix.ros }} (${{ matrix.os }})
     runs-on: ${{ matrix.os }}