Update paniclock.rb becuase string comparison format is deprecated

[morpheus1211]

Calling string comparison format for depends_on macos: is deprecated; using depends_on macos: :sonoma instead.

This solves the warning that Homebrew throws when running (for example) brew update:

Warning: Calling string comparison format for `depends_on macos:` is deprecated! Use `depends_on macos: :sonoma` instead.
Please report this issue to the paniclock/homebrew-tap tap (not Homebrew/* repositories), or even better, submit a PR to fix it:
  /opt/homebrew/Library/Taps/paniclock/homebrew-tap/Casks/p/paniclock.rb:15