AMBARI-12077. HDP: remove ubuntu from the HDP-2.3 repo list (smohanty)

ambari-server/src/main/resources/stacks/HDP/2.3/repos/repoinfo.xml

@@ -53,16 +53,4 @@
       <reponame>HDP-UTILS</reponame>
     </repo>
   </os>
-  <os family="ubuntu12">
-    <repo>
-      <baseurl>http://s3.amazonaws.com/dev.hortonworks.com/HDP/ubuntu12/2.x/updates/2.3.0.0</baseurl>
-      <repoid>HDP-2.3</repoid>
-      <reponame>HDP</reponame>
-    </repo>
-    <repo>
-      <baseurl>http://public-repo-1.hortonworks.com/HDP-UTILS-1.1.0.20/repos/ubuntu12</baseurl>
-      <repoid>HDP-UTILS-1.1.0.20</repoid>
-      <reponame>HDP-UTILS</reponame>
-    </repo>
-  </os>
 </reposinfo>