Merge pull request #40175 from chinmayi-chandrasekar/BZ1995934_add_ipv6_prereq

BZ1995934: add the IPv6 prereq for converting to dual stack

Author: Christopher Tauchen

modules/nw-dual-stack-convert.adoc

@@ -13,6 +13,7 @@ After converting to dual-stack networking only newly created pods are assigned I
 * You installed the OpenShift CLI (`oc`).
 * You are logged in to the cluster with a user with `cluster-admin` privileges.
 * Your cluster uses the OVN-Kubernetes cluster network provider.
+* The cluster nodes have IPv6 addresses.
 
 .Procedure