Add note in `upstream.rbi`.
Add note in `upstream.rbi`.

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