QmdDesigner: Enable rendering single items again for render puppet

Change the form editor rendering to be done by item basis instead of
just rendering the entire scene (unified rendering).

Fixes: QDS-2933
Change-Id: I999cbc834791bc6e96334eab8273d97e4f58975f
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>
Reviewed-by: Mahmoud Badri <mahmoud.badri@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>

share/qtcreator/qml/qmlpuppet/qml2puppet/instances/qt5rendernodeinstanceserver.cpp

@@ -102,9 +102,6 @@ void Qt5RenderNodeInstanceServer::collectItemChangesAndSendChangeCommands()
             clearChangedPropertyList();
 
             if (Internal::QuickItemNodeInstance::unifiedRenderPath()) {
-                /* QQuickItem::grabToImage render path */
-                /* TODO implement QQuickItem::grabToImage based rendering */
-                /* sheduleRootItemRender(); */
                 if (windowDirty)
                     nodeInstanceClient()->pixmapChanged(createPixmapChangedCommand({rootNodeInstance()}));
             } else {