TRIVIAL: fix ghcr push workflow (#11)

Author: svenRelovsky

.github/workflows/docker.yml

@@ -31,7 +31,7 @@ jobs:
         id: docker_meta
         uses: docker/metadata-action@v4
         with:
-          images: wandera/jool
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
       - name: Build and push
         uses: docker/build-push-action@v2
         with: