Remove unneeded window attribute in custom paint widget

* This was having some unpleasant knock-on effects in Qt that caused other
  controls in the panels to fail to render properly.

qrenderdoc/Widgets/CustomPaintWidget.cpp

@@ -49,7 +49,6 @@ CustomPaintWidget::CustomPaintWidget(QWidget *parent) : QWidget(parent)
   m_Tag = QFormatStr("custompaint%1").arg((uintptr_t) this);
 
   setAttribute(Qt::WA_OpaquePaintEvent);
-  setAttribute(Qt::WA_PaintOnScreen);
 
   m_Dark = Formatter::DarkCheckerColor();
   m_Light = Formatter::LightCheckerColor();