fix documentation (bug #3127)

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@4541 65c4cc65-6c06-0410-ace0-fbb531ad65f3

configs/sip.conf.sample

@@ -145,7 +145,6 @@ srvlookup=yes			; Enable DNS SRV lookups on outbound calls
 ; context                     context
 ; permit                      permit
 ; deny                        deny
-; auth                        auth
 ; secret                      secret
 ; md5secret                   md5secret
 ; dtmfmode                    dtmfmode