Update r-server-overview.md

ML Services update

Author: ashishthaps1

articles/hdinsight/r-server/r-server-overview.md

@@ -7,7 +7,7 @@ ms.author: hrasheed
 ms.reviewer: jasonh
 ms.custom: hdinsightactive
 ms.topic: overview
-ms.date: 06/12/2019
+ms.date: 02/10/2020
 #Customer intent: As a developer I want to have a basic understanding of Microsoft's implementation of machine learning in Azure HDInsight so I can decide if I want to use it rather than build my own cluster.
 ---
 
@@ -46,6 +46,9 @@ ML Services in HDInsight provides the following benefits:
 
   Individuals embarking on the journey of making their applications intelligent or simply wanting to learn the new world of AI and machine learning, need the right resources to help them get started. In addition to this documentation, Microsoft provides several learning resources and has engaged several training partners to help you ramp up and become productive quickly.
 --->
+> [!NOTE]  
+> ML Services cluster type in HDInsight is only supported in HDInsight 3.6. HDInsight 3.6 is scheduled to retire on Dec 31st 2020.
+
 
 ## Key features of ML Services on HDInsight