Follow-up to commit 69555b364d, using
QTimeZone::isTimeZoneIdAvailable() instead of trying to construct an
ad-hoc test for known unknonwn zone IDs.
Reopens: QTBUG-102187
Fixes: QTBUG-102187
Change-Id: I36ff4f1dfbc4035d73df5b8fd68376c1bc9641e1
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>