Update slack-beta from 4.9.0-beta1 to 4.9.0-beta2 (#9461)
Update slack-beta from 4.9.0-beta1 to 4.9.0-beta2 (#9461)


404NetworkError/homebrew-versions,pkq/homebrew-versions,pkq/homebrew-versions,caskroom/homebrew-versions,404NetworkError/homebrew-versions,caskroom/homebrew-versions,mahori/homebrew-cask-versions