Added a note for restricted network for graph data image push

Author: snarayan-redhat

modules/update-service-graph-data.adoc

@@ -29,3 +29,8 @@ $ podman build -f ./Dockerfile -t registry.example.com/openshift/graph-data:late
 ----
 $ podman push registry.example.com/openshift/graph-data:latest
 ----
++
+[NOTE]
+====
+For pushing a graph data image to a local registry in a restricted network, copy the graph-data container image created in the previous step to a repository that is accessible to the OpenShift Update Service. You can run `oc image mirror --help` for available options.
+====