doc this string

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@6811 d0543943-73ff-0310-b7d9-9358b9ac24b2

conf/sip_profiles/default.xml

@@ -15,6 +15,7 @@
   </domains>
   
   <settings>
+    <!-- <param name="user-agent-string" value="FreeSWITCH Rocks!"/> -->
     <param name="debug" value="0"/>
     <param name="sip-trace" value="no"/>
     <param name="context" value="public"/>