only release docker builds when we make a release

Author: vertti

.github/workflows/docker.yml

@@ -53,7 +53,7 @@ jobs:
         with:
           context: .
           platforms: linux/amd64,linux/arm64
-          push: true
+          push: ${{ github.event_name == 'release' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha