[FAB-15994] What's New v1.4.2 edits

Clarify that Kafka to Raft migration is available as of v1.4.2.

FAB-15994 #done

Change-Id: I01252b948c6fbbd0a7c0b9a63309b898c26afa29
Signed-off-by: David Enyeart <enyeart@us.ibm.com>

docs/source/whatsnew.rst

@@ -42,10 +42,6 @@ across the world to contribute nodes to a decentralized ordering service.
   Shows the configuration parameters and considerations when deploying a Raft
   ordering service.
 
-* :doc:`kafka_raft_migration`:
-  If you're a user with a Kafka ordering service, this doc shows the process for
-  migrating to a Raft ordering service.
-
 * :doc:`orderer_deploy`:
   Describes the process for deploying an ordering node, independent of what the
   ordering service implementation will be.
@@ -54,6 +50,10 @@ across the world to contribute nodes to a decentralized ordering service.
   The ability to stand up a sample network using a Raft ordering service has been
   added to this tutorial.
 
+* :doc:`kafka_raft_migration`:
+  If you're a user with a Kafka ordering service, this doc shows the process for
+  migrating to a Raft ordering service. Available since v1.4.2.
+
 Serviceability and operations improvements
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