chan_motif: Correct last commit to use ao2_cleanup to free format cap

This fix applies to 13 and trunk.

ASTERISK-24384 #close
Reported by: Corey Farrell
Review: https://reviewboard.asterisk.org/r/4043/
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Merged revisions 424554 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@424555 65c4cc65-6c06-0410-ace0-fbb531ad65f3