Remove `INode.onReplaced` (leftover from previous redo impl)

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Implementation/SerializableNode.cs

 
         public OnNodeModified onModified { get; set; }
 
-        public OnNodeReplaced onReplaced { get; set; }
-
         public IEnumerable<T> GetInputSlots<T>() where T : ISlot
         {
             return GetSlots<T>().Where(x => x.isInputSlot);

MaterialGraphProject/Assets/GraphFramework/SerializableGraph/Editor/Interfaces/INode.cs

     public interface INode
     {
         OnNodeModified onModified { get; set; }
-        OnNodeReplaced onReplaced { get; set; }
         IGraph owner { get; set; }
         Guid guid { get; }
         Guid RewriteGuid();

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Views/MaterialNodeView.cs

             m_Preview = previewSystem.GetPreview(inNode);
             m_Preview.onPreviewChanged += OnPreviewChanged;
 
-            node.onReplaced += OnReplaced;
-
             // From OnDataChange()
 
             m_PreviewToggle.text = node.previewExpanded ? "▲" : "▼";