Removed useless code

Assets/ScriptableRenderLoop/HDRenderPipeline/Utilities.cs

 #else
                     UnityObject.Destroy(obj);
 #endif
-                obj = null;
             }
         }
 
-            {
-                buffer = null;
-            }
         }
 
         public static string GetFieldPath<TType, TValue>(Expression<Func<TType, TValue>> expr)