completions/zsh: fix broken zsh tab completion for `brew upgrade`
completions/zsh: fix broken zsh tab completion for `brew upgrade`

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