keyword username is not used in iax/iax2

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@1616 65c4cc65-6c06-0410-ace0-fbb531ad65f3

configs/iax.conf.sample

@@ -141,7 +141,6 @@ permit=216.207.245.47/255.255.255.255
 ;
 [demo]
 type=peer
-username=asterisk
 secret=supersecret
 host=216.207.245.47
 ;sendani=no