ical-recurrence: test that an ExceptionDateTimes in another time zone excludes
removeExceptionDatetimes compares DateTime values structurally, so it
only ever excludes an instance when the constructor and the time zone
identifier match exactly.
RFC 5545 constrains the value type of EXDATE to that of DTSTART, but not
the time zone it is given in, so the calendar in this test conforms and
its EXDATE names the second instance unambiguously. It is silently
ignored. Matching should happen on resolved instants instead.