cmd/(outdated,upgrade): Document -g as a shorter --greedy for Casks

[issyl0]

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• Fixes Add indication to help and man pages that "-g" is a valid alias for "--greedy", as well as "brew up" and "brew update" #14682.

[BrewTestBot]

Review period will end on 2023-02-21 at 00:00:00 UTC.

[MikeMcQuaid]

Thanks again again @issyl0!

[BrewTestBot]

Review period skipped due to critical label.