Update chan_agent documentation. Change a | to , as that is now the required way.

(closes issue #11167)
Reported by: eliel
Patches:
      chan_agent.c.patch uploaded by eliel (license 64)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@88974 65c4cc65-6c06-0410-ace0-fbb531ad65f3