TableView is now ready for Qt-5.12. The only thing missing
is documentation, which is currently being written, and on the
way. So remove the temporary labs plugin that used to register
TableView, and register it together with the other QtQuick items.
Change-Id: I7f360eac3934d228904a4133363e336afe0c451a
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@qt.io>
Reviewed-by: Shawn Rutledge <shawn.rutledge@qt.io>