formula_installer: fix pruning of test deps also marked as build
formula_installer: fix pruning of test deps also marked as build

mahori/brew,sjackman/homebrew,Homebrew/brew,konqui/brew,JCount/brew,vitorgalvao/brew,JCount/brew,Homebrew/brew,mahori/brew,EricFromCanada/brew,claui/brew,konqui/brew,EricFromCanada/brew,vitorgalvao/brew,claui/brew,Homebrew/brew,MikeMcQuaid/brew,nandub/brew,sjackman/homebrew,sjackman/homebrew,MikeMcQuaid/brew,reitermarkus/brew,MikeMcQuaid/brew,reitermarkus/brew,vitorgalvao/brew,vitorgalvao/brew,JCount/brew,MikeMcQuaid/brew,reitermarkus/brew,reitermarkus/brew,nandub/brew,claui/brew,nandub/brew,Homebrew/brew,claui/brew,mahori/brew,nandub/brew,konqui/brew,konqui/brew,mahori/brew,EricFromCanada/brew,EricFromCanada/brew,JCount/brew,sjackman/homebrew