Fix skopeo destination url

Previously skopeo tried to push images to e.g.
  docker://docker.mantis.ws/morpho-node/docker.mantis.ws/morpho-node:<tag>
which despite seeming wrong, apparently exited without error
This commit fixes it to push to the correct
  docker://docker.mantis.ws/morpho-node:<tag>
instead

lib/run-nomad-job.nix

@@ -20,7 +20,7 @@ let
         })"
         ${skopeo}/bin/skopeo copy \
           "docker-archive://$storePath" \
-          "docker://${registry}/${repo}/${image.imageName}:${image.imageTag}" \
+          "docker://${registry}/${repo}:${image.imageTag}" \
           --dest-creds "developer:$dockerPassword"
       fi
     '';