[BC] Remove output formats not displaying calendar data

[igneus]

Currently there are some synonym options resulting in the same output

• --format=calendars and --calendars
• --format=easter and --easter

That's unfortunate, because the semantics of --calendars and --easter are quite different from the rest of the --format=... options. --format should only be used to select a formatter operating on any given date range and actually displaying calendar data for that date range (not a listing of supported calendars, which is not dependent on the date range at all, or easter date for a single year). --format=calendars and --format=easter should not be available.