Fix typo on mapping filename
Fix typo on mapping filename

Now the setup.cfg example for extract_messages configuration is equivalent to the command line example.
gutsy/babel,iamshubh22/babel,skybon/babel,jmagnusson/babel,moreati/babel,lepistone/babel,mbirtwell/babel,python-babel/babel,srisankethu/babel,python-babel/babel,st4lk/babel,srisankethu/babel,lepistone/babel,jmagnusson/babel,srisankethu/babel,julen/babel,skybon/babel,upman/babel,mbirtwell/babel,KIT-XXI/babel,moreati/babel,felixonmars/babel,skybon/babel,lepistone/babel,julen/babel,mbirtwell/babel,KIT-XXI/babel,felixonmars/babel,gutsy/babel,mitsuhiko/babel,moreati/babel,hanteng/babel,iamshubh22/babel,gutsy/babel,st4lk/babel,mitsuhiko/babel,KIT-XXI/babel,felixonmars/babel,hanteng/babel,julen/babel,upman/babel,st4lk/babel,mitsuhiko/babel,hanteng/babel,upman/babel,iamshubh22/babel,jmagnusson/babel