Stabilize Test

A slight variance on this number is acceptable, it should be using
extremelyFuzzyCompare like the rest of the checks on that property.

Task-number: QTBUG-35470
Change-Id: I9114a3a5d3bbc3c63253320637f7af1e5f21a896
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>