cask `url do` blocks is deprecated in new version of homebrew

[Wybxc]

When I tried to install nightly version of PlayCover via homebrew, I encountered this issue:

$ brew install --cask playcover-nightly
Error: Calling cask `url do` blocks is disabled! There is no replacement.
Please report this issue:
  https://docs.brew.sh/Troubleshooting

The formula definition needs to be modified to work with new version of homebrew.

Maybe useful reference: https://github.com/orgs/Homebrew/discussions/5879#discussioncomment-11873759