Set simplePalette on staticWidget in tst_QWidget::optimizedResizeMove

It was forgotten to assign a simple palette to this object in
1576f827214cca8a2233f3c81e7d0e3d89eb8007

This patch adds the missing line.

Pick-to: 6.4
Change-Id: I0acf765d9646ecc8d49791d96b5ea910e11997fe
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp

@@ -4549,6 +4549,7 @@ void tst_QWidget::optimizedResizeMove()
     parent.resize(400, 400);
 
     StaticWidget staticWidget(&parent);
+    staticWidget.setPalette(simplePalette());
     staticWidget.gotPaintEvent = false;
     staticWidget.move(150, 150);
     staticWidget.resize(150, 150);