QmlDesigner: Do not move delegate items

Items that are not in a list should not be movable.
This effects items in back or front in flipable or styling items.

Change-Id: I829aaca7b838b5ea21b96a18c9bfd64c9ae8286d
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/qmldesigner/designercore/model/qmlitemnode.cpp

@@ -371,6 +371,8 @@ bool itemIsMovable(const ModelNode &modelNode)
     if (modelNode.metaInfo().isSubclassOf("QtQuick.Controls.Tab"))
         return false;
 
+    if (!modelNode.parentProperty().isNodeListProperty())
+        return false;
 
     return NodeHints::fromModelNode(modelNode).isMovable();
 }