Use new sarif fomat for Trivy (#183)

Author: lucacome

.github/workflows/ci.yml

@@ -190,8 +190,7 @@ jobs:
         continue-on-error: true
         with:
           image-ref: ghcr.io/nginxinc/nginx-kubernetes-gateway:${{ steps.meta.outputs.version }}
-          format: 'template'
-          template: '@/contrib/sarif.tpl'
+          format: 'sarif'
           output: 'trivy-results-nginx-kubernetes-gateway.sarif'
           ignore-unfixed: 'true'
       - name: Upload Trivy scan results to GitHub Security tab