cli_parser: undefine OpenStruct instance tap.
cli_parser: undefine OpenStruct instance tap.

Undefine `tap` to allow `--tap` arguments to work as expected.

claui/brew,sjackman/homebrew,ilovezfs/brew,MikeMcQuaid/brew,DomT4/brew,mahori/brew,maxim-belkin/brew,EricFromCanada/brew,DomT4/brew,mgrimes/brew,hanxue/linuxbrew,vitorgalvao/brew,reitermarkus/brew,sjackman/homebrew,claui/brew,MikeMcQuaid/brew,konqui/brew,ilovezfs/brew,sjackman/homebrew,sjackman/homebrew,JCount/brew,mahori/brew,Linuxbrew/brew,konqui/brew,nandub/brew,reitermarkus/brew,Homebrew/brew,vitorgalvao/brew,hanxue/linuxbrew,claui/brew,mgrimes/brew,nandub/brew,hanxue/linuxbrew,maxim-belkin/brew,reitermarkus/brew,maxim-belkin/brew,mahori/brew,mahori/brew,konqui/brew,Linuxbrew/brew,vitorgalvao/brew,JCount/brew,ilovezfs/brew,MikeMcQuaid/brew,MikeMcQuaid/brew,JCount/brew,DomT4/brew,nandub/brew,Homebrew/brew,claui/brew,Linuxbrew/brew,EricFromCanada/brew,Linuxbrew/brew,JCount/brew,vitorgalvao/brew,reitermarkus/brew,Homebrew/brew,EricFromCanada/brew,nandub/brew,EricFromCanada/brew,DomT4/brew,konqui/brew,mgrimes/brew,Homebrew/brew