Calling the appcast stanza is deprecated (macOS)

[andreatitolo]

Describe the bug

During brew update:

Warning: Calling the `appcast` stanza is deprecated! Use the `livecheck` stanza instead.
Please report this issue to the koordinates/kart tap (not Homebrew/brew or Homebrew/homebrew-core), or even better, submit a PR to fix it:
  /opt/homebrew/Library/Taps/koordinates/homebrew-kart/Casks/kart.rb:7

[rcoup]

@andreatitolo thanks, will get this sorted

---

For my reference:

• livecheck documentation
• There's plenty of examples of Casks being updated from appcast to livecheck on Github

[andreatitolo]

Thank you! :)