Add RHV to supported migrations

- https://issues.redhat.com/browse/OSDOCS-1809

Author: jboxman

modules/nw-ovn-kubernetes-migration-about.adoc

@@ -14,6 +14,7 @@ A migration to the OVN-Kubernetes cluster network provider is supported on the f
 * Google Cloud Platform (GCP)
 * Microsoft Azure
 * {rh-openstack-first}
+* {rh-virtualization-first}
 * VMware vSphere
 
 [id="considerations-migrating-ovn-kubernetes-network-provider_{context}"]