Comment out old artistic nodes

MaterialGraphProject/Assets/NewNodes/Editor/Keep/ColorBalanceNode.cs

 using System.Reflection;
 using UnityEngine;
 
-namespace UnityEditor.ShaderGraph
+/*namespace UnityEditor.ShaderGraph
 {
     [Title("Art", "Adjustments", "ColorBalance")]
     public class ColorBalanceNode : CodeFunctionNode
 ";
         }
     }
-}
+}*/

MaterialGraphProject/Assets/NewNodes/Editor/Keep/LevelsNode.cs

 using System.Collections.Generic;
 using System.Reflection;
 
-namespace UnityEditor.ShaderGraph
+/*namespace UnityEditor.ShaderGraph
 {
     [Title("Art", "Adjustments", "Levels")]
     public class LevelsNode : CodeFunctionNode
 ";
         }
     }
-}
+}*/