doc: remove outdated documentation for completion (#99)
doc: remove outdated documentation for completion (#99)

By the commit edf000e4cd30c3626ccc28c52ed32f2d84a200dd, bash and zsh
completion scripts have been moved to `etc/bash_completion.d/brew` and
`share/zsh/site-functions/_brew`, respectively. Now completion will be
done automatically without any trick.
bfontaine/brew,toonetown/homebrew,EricFromCanada/brew,hanxue/linuxbrew,muellermartin/dist,gregory-nisbet/brew,MikeMcQuaid/brew,AnastasiaSulyagina/brew,reitermarkus/brew,maxim-belkin/brew,claui/brew,palxex/brew,gordonmcshane/homebrew,mistydemeo/homebrew,jmsundar/brew,jmsundar/brew,muellermartin/dist,DomT4/brew,zmwangx/brew,palxex/brew,mahori/brew,Homebrew/brew,konqui/brew,aw1621107/brew,JCount/brew,ilovezfs/brew,mahori/brew,konqui/brew,gordonmcshane/homebrew,staticfloat/brew,mgrimes/brew,staticfloat/brew,mgrimes/brew,zmwangx/brew,maxim-belkin/brew,nandub/brew,reelsense/brew,nandub/brew,AnastasiaSulyagina/brew,nandub/brew,sjackman/homebrew,Homebrew/brew,mistydemeo/homebrew,pseudocody/brew,sjackman/homebrew,mistydemeo/homebrew,alyssais/brew,amar-laksh/brew_sudo,ilovezfs/brew,palxex/brew,AnastasiaSulyagina/brew,sjackman/homebrew,mahori/brew,Linuxbrew/brew,alyssais/brew,Linuxbrew/brew,claui/brew,rwhogg/brew,JCount/brew,Linuxbrew/brew,Homebrew/brew,pseudocody/brew,DomT4/brew,MikeMcQuaid/brew,DomT4/brew,tonyg/homebrew,pseudocody/brew,staticfloat/brew,bfontaine/brew,mgrimes/brew,EricFromCanada/brew,gregory-nisbet/brew,sjackman/homebrew,claui/brew,reitermarkus/brew,claui/brew,konqui/brew,toonetown/homebrew,gordonmcshane/homebrew,bfontaine/brew,Homebrew/brew,hanxue/linuxbrew,zmwangx/brew,JCount/brew,MikeMcQuaid/brew,alyssais/brew,tonyg/homebrew,nandub/brew,gregory-nisbet/brew,maxim-belkin/brew,amar-laksh/brew_sudo,reitermarkus/brew,mahori/brew,aw1621107/brew,MikeMcQuaid/brew,vitorgalvao/brew,muellermartin/dist,reitermarkus/brew,EricFromCanada/brew,EricFromCanada/brew,ilovezfs/brew,vitorgalvao/brew,amar-laksh/brew_sudo,tonyg/homebrew,reelsense/brew,reelsense/brew,toonetown/homebrew,vitorgalvao/brew,rwhogg/brew,JCount/brew,aw1621107/brew,Linuxbrew/brew,DomT4/brew,hanxue/linuxbrew,jmsundar/brew,konqui/brew,vitorgalvao/brew,rwhogg/brew