install: remove not updated warning.
install: remove not updated warning.

This is no longer relevant after moving to taps/tags and if ever
re-added it should probably target homebrew/core.

Fixes #1194.

DomT4/brew,konqui/brew,muellermartin/dist,mahori/brew,reitermarkus/brew,vitorgalvao/brew,maxim-belkin/brew,Linuxbrew/brew,claui/brew,Homebrew/brew,vitorgalvao/brew,bfontaine/brew,sjackman/homebrew,reelsense/brew,tonyg/homebrew,palxex/brew,alyssais/brew,JCount/brew,pseudocody/brew,tonyg/homebrew,sjackman/homebrew,vitorgalvao/brew,aw1621107/brew,pseudocody/brew,mgrimes/brew,jmsundar/brew,zmwangx/brew,nandub/brew,rwhogg/brew,hanxue/linuxbrew,reitermarkus/brew,palxex/brew,mahori/brew,EricFromCanada/brew,aw1621107/brew,MikeMcQuaid/brew,amar-laksh/brew_sudo,maxim-belkin/brew,sjackman/homebrew,JCount/brew,bfontaine/brew,mgrimes/brew,jmsundar/brew,amar-laksh/brew_sudo,MikeMcQuaid/brew,EricFromCanada/brew,MikeMcQuaid/brew,muellermartin/dist,DomT4/brew,mahori/brew,palxex/brew,rwhogg/brew,JCount/brew,nandub/brew,claui/brew,pseudocody/brew,alyssais/brew,reitermarkus/brew,hanxue/linuxbrew,MikeMcQuaid/brew,jmsundar/brew,mgrimes/brew,Homebrew/brew,nandub/brew,vitorgalvao/brew,gregory-nisbet/brew,EricFromCanada/brew,maxim-belkin/brew,aw1621107/brew,konqui/brew,Homebrew/brew,amar-laksh/brew_sudo,zmwangx/brew,bfontaine/brew,zmwangx/brew,ilovezfs/brew,Linuxbrew/brew,ilovezfs/brew,Linuxbrew/brew,muellermartin/dist,nandub/brew,EricFromCanada/brew,reelsense/brew,konqui/brew,DomT4/brew,rwhogg/brew,ilovezfs/brew,sjackman/homebrew,hanxue/linuxbrew,DomT4/brew,Linuxbrew/brew,reelsense/brew,Homebrew/brew,JCount/brew,alyssais/brew,reitermarkus/brew,konqui/brew,mahori/brew,gregory-nisbet/brew,gregory-nisbet/brew,claui/brew,tonyg/homebrew,claui/brew