ci/cd: testing needs to use the same commit as the building workflow

.github/workflows/linux-test-packages.yml

@@ -26,7 +26,7 @@ jobs:
         uses: 'actions/checkout@v3'
         with:
           path: '${{ env.BASE_DIR }}/repos/monitoring-plugins'
-          ref: '${{ inputs.package-version || github.ref }}'
+          ref: '${{ github.event.workflow_run.head_commit }}'
 
       # using this instead of the official `download-artifact` action since this allows cross-workflow
       - name: 'download the monitoring-plugins-linux-packages artifact'