OCPBUGS-7592: adds clarification for IPv6 support

Author: xenolinux

modules/installing-ocp-agent.adoc

@@ -128,6 +128,7 @@ platform:
     - 192.168.11.4
     - 2001:DB8::5
 ----
+IPv6 is supported only on bare metal platforms.
 ====
 
 . Create the `agent-config.yaml` file:
@@ -268,4 +269,5 @@ networking:
   - fd03::/112
   networkType: OVNKubernetes
 ----
+IPv6 is supported only on bare metal platforms.
 ====