Add fix for Snyk sarif file incompatibility

Null value is not supported. Issue reported at github/codeql-action#2187

.github/workflows/snyk-container.yml

@@ -49,6 +49,9 @@ jobs:
       with:
         image: patrikjuvonen/docker-nginx-http3:snyk-ci
         args: --file=Dockerfile
+    # Patch for https://github.com/github/codeql-action/issues/2187
+    - name: Replace security-severity undefined for license-related findings
+      run: sed -i 's/"security-severity": "null"/"security-severity": "0"/g' snyk.sarif
     - name: Upload result to GitHub Code Scanning
       uses: github/codeql-action/upload-sarif@v3
       with: