fix: issue with truffle hog (#612)

adapted out of db-ux-design-system/icon-font-tools#353

Author: mfranzke

.github/workflows/00-scan-secrets.yml

@@ -18,6 +18,7 @@ jobs:
 
       - name: 🐷 TruffleHog OSS
         uses: trufflesecurity/trufflehog@main
+        if: ${{ github.event.pull_request != null }} # only scan on pull-requests
         with:
           path: ./
           base: ${{ steps.extract_branch.outputs.branch-name }}