Remove another copied source file on "make clean".

(closes issue #11137)
Reported by: IgorG
Patches: 
      addonclean-87971-1.patch uploaded by IgorG (license 20)


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@88062 65c4cc65-6c06-0410-ace0-fbb531ad65f3