Actually push Docker images (#810)

Author: kyleconroy

.github/workflows/docker.yml

@@ -30,3 +30,4 @@ jobs:
           org.opencontainers.image.source=${{ github.event.repository.html_url }}
           org.opencontainers.image.created=${{ steps.prep.outputs.created }}
           org.opencontainers.image.revision=${{ github.sha }}
+        push: true