Fix the sed expression
Fix the sed expression

gulopine/heroku-buildpack-tex,milos-korenciak/heroku-buildpack-tex,milos-korenciak/heroku-buildpack-tex,colonyamerican/heroku-buildpack-tex,HansKayaert/tex-buildpack-Heroku,Thermondo/heroku-buildpack-tex,mezis/heroku-buildpack-tex,CalebMorris/tex-packages-buildpack,milos-korenciak/heroku-buildpack-tex,wccinc/heroku-buildpack-tex,milos-korenciak/heroku-buildpack-tex,heungju/heroku-buildpack-tex,colonyamerican/tex-packages-buildpack,GeorgeNagel/heroku-tex