tests|qtquick|Windows: Stabilize a test

The warning is benign and unrelated to anything kddw is doing

tests/Testing.cpp

@@ -66,6 +66,7 @@ static bool shouldBlacklistWarning(const QString &msg, const QString &category)
         || msg.contains(QLatin1String("Testing::"))
         || msg.contains(QLatin1String("outside any known screen, using primary screen"))
         || msg.contains(QLatin1String("Populating font family aliases took"))
+        || msg.contains(QLatin1String("QSGThreadedRenderLoop: expose event received for window"))
 #ifdef KDDOCKWIDGETS_QTQUICK
     // TODO: Fix later, not important right now
     || msg.contains(QLatin1String("Binding loop detected for property"))