Fix push event

Currently, tag (release) builds of the Docker image wouldn't be pushed.

Author: fwcd

.github/workflows/docker.yml

@@ -33,6 +33,6 @@ jobs:
         with:
           context: .
           platforms: linux/amd64,linux/arm64/v8
-          push: ${{ github.ref == 'refs/heads/main' }}
+          push: ${{ github.event_name != 'pull_request' }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}