udptl: Dead code elimination. ast_udptl_bridge was not used.

Removing dead code starting with ast_udptl_bridge() eliminated the code in
this change.

Note: This code has actually been dead since Asterisk v1.4 when it was
first put in.

Review: https://reviewboard.asterisk.org/r/3079/
........

Merged revisions 404354 from http://svn.asterisk.org/svn/asterisk/branches/12


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@404355 65c4cc65-6c06-0410-ace0-fbb531ad65f3