Remove needless inheritance from MaterialNodePresenter in GraphControlPresenter

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Drawing/Presenters/GraphControlPresenter.cs

 namespace UnityEditor.MaterialGraph.Drawing
 {
     [Serializable]
-    public abstract class GraphControlPresenter : MaterialNodePresenter
+    public abstract class GraphControlPresenter : ScriptableObject
     {
         public INode node { get; private set; }
 

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

 
         void InvalidateUIIfNeedsTime(TimerState timerState)
         {
-            var node = GetPresenter<MaterialNodePresenter>();
-            if (node.requiresTime)
+            var nodePresenter = GetPresenter<MaterialNodePresenter>();
+            if (nodePresenter.requiresTime)
-                node.OnModified(ModificationScope.Node);
+                nodePresenter.OnModified(ModificationScope.Node);
                 UpdatePreviewTexture(m_CurrentPreview);
             }
         }