Remove the compare method in the QVariant::Handler struct. Rely
on the generic support provided by QMetaType instead.
[ChangeLog][Important Behavior Changes][QVariant] QVariant will now use builtin support in
QMetaType to compare its content. This implies a behavioral change
for some graphical types like QPixmap, QImage and QIcon that will
never compare equal in Qt 6 (as they do not have a comparison
operator).
Change-Id: I30a6e7116c89124d11ed9052537cecc23f78116e
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
50c96c17b6