Fix condition

.github/workflows/docker-publish.yml

@@ -87,6 +87,7 @@ jobs:
       # transparency data even for private images, pass --force to cosign below.
       # https://github.com/sigstore/cosign
       - name: Sign the published Docker image
+        if: github.event_name != 'pull_request'
         env:
           # https://docs.github.com/en/actions/security-guides/security-hardening-for-github-actions#using-an-intermediate-environment-variable
           TAGS: ${{ steps.meta.outputs.tags }}