Removed uneeded Fog enum

MaterialGraphProject/Assets/UnityShaderEditor/Editor/Data/Nodes/Input/Scene/FogNode.cs

 
 namespace UnityEditor.ShaderGraph
 {
-    public enum FogMode
-    {
-        Linear,
-        Exponential,
-        ExponentialSquared
-    };
-
     [Title("Input", "Scene", "Fog")]
     public class FogNode : AbstractMaterialNode, IGeneratesBodyCode, IMayRequirePosition
     {