Update slack-beta from 3.4.1 to 3.4.2-beta4 (#7397)
Update slack-beta from 3.4.1 to 3.4.2-beta4 (#7397)


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