Mark QAbstractTextDocumentLayout test as insignificant

Mark QAbstractTextDocumentLayout test as insignificant

This test fails on some setups and a pending critical change
causes the existing bug to trigger in CI. To avoid blocking
other changes because of this bug, it's been marked as
insignificant until such a time when it can be fixed.

Change-Id: Ide41f7b1c76209f9c05f95f996b2364d5dea5e67
Reviewed-by: Liang Qi <liang.qi@digia.com>
Reviewed-by: Andy Shaw <andy.shaw@digia.com>
(cherry picked from commit 02032fb229e4a26b2848db60e90820e2daeb3363)
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>