doc improvement

git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@9870 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/resources/hudson/model/UpdateCenter/main.jelly

@@ -2,6 +2,8 @@
   If necessary, ask the client to fetch update-center data file for us.
   This allows us to avoid proxy related configuration on the server,
   and instead piggy-back on user connection.
+
+  This file is pulled into the layout.jelly
 -->
 <j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form">
   <j:if test="${it.due}">