QmlDesigner: Make alternative icon engine HighDPI-aware

Change-Id: Ib1c757aac7cf7a963b2912f98fc5cd403f667ed7
Reviewed-by: Aleksei German <aleksei.german@qt.io>
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/libs/utils/stylehelper.cpp

@@ -563,7 +563,7 @@ QIcon StyleHelper::getIconFromIconFont(const QString &fontName, const QString &i
             pixmap.fill(Qt::transparent);
 
             QFont font(fontName);
-            font.setPixelSize(fontSize * dpr);
+            font.setPixelSize(fontSize);
 
             QPainter painter(&pixmap);
             painter.save();