test-bot: use IO#read instead of IO#gets
test-bot: use IO#read instead of IO#gets

IO#gets will only return for every new lines, which will be bad for
`brew install` since we print dots in single line.

Closes Homebrew/homebrew#44264.

Signed-off-by: Xu Cheng <9a05244150b861e40c78843b801eed71bca54eac@me.com>

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