fix: remove superfluous push

Author: lionello

.github/workflows/docker-image-release.yml

@@ -36,8 +36,6 @@ jobs:
     runs-on: ubuntu-latest
     environment: release
     steps:
-      - uses: actions/checkout@v4
-
       - name: Set IMAGE_TAG
         run: echo "IMAGE_TAG=$(echo $GITHUB_SHA | cut -c 1-7)" >> $GITHUB_ENV
 
@@ -82,8 +80,6 @@ jobs:
       - name: Authenticate to GCR
         run: |
           gcloud auth --project=${GCP_PROJECT} configure-docker ${GCP_REGION}-docker.pkg.dev
-          docker build . --file Dockerfile --tag ${{ env.GCP_REGION }}-docker.pkg.dev/defang-io/public/railpack-builder:${{ env.IMAGE_TAG }}
-          docker push ${{ env.GCP_REGION }}-docker.pkg.dev/defang-io/public/railpack-builder:${{ env.IMAGE_TAG }}
 
       - name: Build and push multi-arch Docker image
         uses: docker/build-push-action@v6