Make livecheck audit mandatory for versioned casks.

[reitermarkus]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew typecheck with your changes locally?
• Have you successfully run brew tests with your changes locally?

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Some livechecks work using the auto-detected strategy, but we don't have a way to know the difference between a missing livecheck block and implicitly using the auto-detected strategy.

For now, casks with an existing appcast are still skipped.

[BrewTestBot]

Review period will end on 2021-03-23 at 00:00:00 UTC.

[BrewTestBot]

Review period ended.