ci: only push if is not a fork (#446)

Author: gusinacio

.github/workflows/containers.yml

@@ -83,6 +83,6 @@ jobs:
         uses: docker/build-push-action@4f58ea79222b3b9dc2c8bbdd6debcef730109a75 # v6
         with:
           context: ./
-          push: true
+          push: ${{ github.event.pull_request.head.repo.full_name == github.repository }}
           tags: ${{ steps.meta.outputs.tags }}
           file: Dockerfile.${{ matrix.target }}