Don't use matrix when we don't need it

Signed-off-by: Emerson Knapp <[email protected]>

.github/workflows/lint.yml

@@ -79,12 +79,8 @@ jobs:
             shared_queues_vendor
 
   ament_lint_cppcheck: # cppcheck linter (disabled for rosbag2_transport)
-    name: ament_${{ matrix.linter }}
+    name: ament_cppcheck
     runs-on: ubuntu-latest
-    strategy:
-      fail-fast: false
-      matrix:
-          linter: cppcheck
     container:
       image: rostooling/setup-ros-docker:ubuntu-focal-ros-foxy-ros-base-testing-latest
     steps:
@@ -93,7 +89,7 @@ jobs:
     - uses: actions/checkout@v2
     - uses: ros-tooling/[email protected]
       with:
-        linter: ${{ matrix.linter }}
+        linter: cppcheck
         distribution: foxy
         package-name: |
             rosbag2_compression