cmd/install: fix --keep-tmp description.
cmd/install: fix --keep-tmp description.

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