Testconfig: Restoring qt.tests.insignificant property to qtqa

Due to fact that qt tests weren't executed for qtqa submodule for
some time, one removed the qt.tests.insignificant property while the
tests were concidered be passing. Apparently the tests have never
passed, so restoring the property.

Task-number: QTQAINFRA-708
Change-Id: I13977b3bbf8bbff3002d5d6b65b49a5b084b3330
Reviewed-by: Sergio Ahumada <sergio.ahumada@digia.com>