Only push to docker hub on default branch

.github/workflows/docker-release.yml

@@ -5,9 +5,6 @@ jobs:
 
   build:
     name: Docker build and push
-    # Only run on default branch.
-    if: >
-      ${{ github.ref == format('refs/heads/{0}', github.event.repository.default_branch) }}
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v3
@@ -32,7 +29,8 @@ jobs:
       with:
         file: Dockerfile
         builder: ${{ steps.buildx.outputs.name }}
-        push: true
+        # Only push on default branch.
+        push: ${{ github.ref == format('refs/heads/{0}', github.event.repository.default_branch) }}
         context: .
         platforms: linux/amd64,linux/arm64
         labels: |