Update microsoft-remote-desktop-beta to 10.2.8.1570,269 (#7038)
Update microsoft-remote-desktop-beta to 10.2.8.1570,269 (#7038)

Squashed and auto-merged via `brew cask automerge`.
lantrix/homebrew-versions,caskroom/homebrew-versions,rogeriopradoj/homebrew-versions,rogeriopradoj/homebrew-versions,lantrix/homebrew-versions,pkq/homebrew-versions,Ngrd/homebrew-versions,mahori/homebrew-cask-versions,victorpopkov/homebrew-versions,victorpopkov/homebrew-versions,caskroom/homebrew-versions,404NetworkError/homebrew-versions,404NetworkError/homebrew-versions,Ngrd/homebrew-versions,mahori/homebrew-versions,pkq/homebrew-versions