DateTimeFormat/constructor-options-calendar-islamic-fallback.js should allow other fallback values

[FrankYFTang]

This test test/intl402/DateTimeFormat/constructor-options-calendar-islamic-fallback.js is incorrect. The defintion of AvailableCalendars in https://tc39.es/proposal-intl-era-monthcode/#sup-availablecalendars
is "The List must include the Calendar Type value of every row of Table 1, except the header row." It does said it ONLY include those listed in that Table. so the return list may also include "islamic" and "islamic-rgsa" and therefore the test is incorrect.