Update slack-beta from 4.8.0-beta1 to 4.8.0 (#9363)
Update slack-beta from 4.8.0-beta1 to 4.8.0 (#9363)


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