The current casks audit is very noisy in the no-op case (i.e. no errors)
https://github.com/Homebrew/brew/pull/10234/checks?check_run_id=1655630568#step:15:7
This means when there are errors and you're querying all casks it's
pretty hard to quickly identify the problems.
This commit silences the `passing`, `warning` and header/summary output
when you're querying all casks (rather than a specific cask or tap).
This is more consistent with `brew audit` for formulae which is silent
unless there are audit failures.
