Mark QGlyphRun and QStaticText tests as insignificant on Linux

Mark QGlyphRun and QStaticText tests as insignificant on Linux

These tests have been failing on certain setups for a while,
but some new critical changes causes the failure to trigger
on the CI system as well. We mark them as insignificant until
they can be fixed.

Change-Id: I467e7030c55d6f23515275b4062c17068d2b688c
Reviewed-by: Andy Shaw <andy.shaw@digia.com>
(cherry picked from commit 04f25ac46ca0956dfd1209b14a1eee9e2e1274c2)
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>