pjsip: Remove "contact" type from pjsip.conf.sample

The "contact" object is not meant to be configured from the pjsip.conf
configuration file. It is meant to be created as a result of a registration
and stored elsewhere.

ASTERISK-24085 #close
Reported by: Rusty Newton
........

Merged revisions 431860 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@431861 65c4cc65-6c06-0410-ace0-fbb531ad65f3