ci: fix tag and push steps

Author: pythoninthegrass

.github/workflows/docker.yml

@@ -97,7 +97,7 @@ jobs:
             type=semver,pattern={{major}}.{{minor}}
             type=semver,pattern={{major}}
             type=sha
-            type=raw,value=latest,enable={{is_default_branch}}
+            type=raw,value=latest,enable=${{ github.ref == format('refs/heads/main') }}
 
       - name: Setup QEMU
         uses: docker/setup-qemu-action@v3
@@ -110,6 +110,7 @@ jobs:
         with:
           context: .
           file: ./${{ matrix.dockerfile }}
+          push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=registry,ref=${{ env.REGISTRY_URL }}/${{ env.REGISTRY_USER }}/${{ steps.image_name.outputs.IMAGE }}:buildcache