Merge pull request #237 from Unity-Technologies/disable-resizing-in-preview-node

[FIX] Disabled the resizing of preview node.

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

 
             SetPosition(new Rect(node.drawState.position.x, node.drawState.position.y, 0, 0));
 
-            if (node is PreviewNode)
+            /*if (node is PreviewNode)
-            }
+            }*/
 
             m_PortInputContainer.SendToBack();
             if (node.hasPreview)