Don't run docker login for pull requests in docker-miminal workflow

.github/workflows/docker-minimal.yml

@@ -31,6 +31,7 @@ jobs:
         with:
           platforms: ${{ env.PLATFORMS }}
       - name: Login to Docker
+        if: ${{ github.event.pull_request != true }}
         uses: docker/login-action@v3
         with:
           username: ${{ secrets.DOCKER_USERNAME }}