bintray: fix typo in it comment
bintray: fix typo in it comment

non-existant -> non-existent
vitorgalvao/brew,konqui/brew,Homebrew/brew,nandub/brew,EricFromCanada/brew,claui/brew,nandub/brew,reitermarkus/brew,reitermarkus/brew,nandub/brew,Homebrew/brew,Homebrew/brew,sjackman/homebrew,MikeMcQuaid/brew,JCount/brew,vitorgalvao/brew,sjackman/homebrew,EricFromCanada/brew,MikeMcQuaid/brew,MikeMcQuaid/brew,nandub/brew,konqui/brew,JCount/brew,reitermarkus/brew,konqui/brew,reitermarkus/brew,EricFromCanada/brew,JCount/brew,MikeMcQuaid/brew,sjackman/homebrew,claui/brew,konqui/brew,vitorgalvao/brew,claui/brew,claui/brew,EricFromCanada/brew,Homebrew/brew,JCount/brew,sjackman/homebrew,vitorgalvao/brew