AMI Docs: Fix Status channel parameter optionality

........

Merged revisions 421442 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 421443 from http://svn.asterisk.org/svn/asterisk/branches/11
........

Merged revisions 421444 from http://svn.asterisk.org/svn/asterisk/branches/12
........

Merged revisions 421445 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@421446 65c4cc65-6c06-0410-ace0-fbb531ad65f3