Add required version for cluster restore (#1096)

Author: kbatuigas

modules/manage/partials/whole-cluster-restore.adoc

@@ -69,6 +69,7 @@ ifdef::env-kubernetes[. <<Verify that the cluster restore is complete>>.]
 
 You must have the following:
 
+- Redpanda v23.3 or later on both source and target clusters.
 - xref:{link-tiered-storage}[Tiered Storage] enabled on the source cluster.
 - Physical or virtual machines on which to deploy the target cluster.