Fix compile loop in vfxoperator (#61)

Author: iTris666

com.unity.visualeffectgraph/Editor/Models/Operators/VFXSubgraphOperator.cs

@@ -237,13 +237,6 @@ protected override VFXExpression[] BuildExpression(VFXExpression[] inputExpressi
                 outputExpressions.AddRange(param.inputSlots[0].GetExpressionSlots().Select(t => t.GetExpression()));
             }
 
-            foreach (var param in parameters)
-            {
-                param.ResetOutputValueExpression();
-            }
-
-            VFXSubgraphUtility.TransferExpressionToParameters(backedUpExpressions, parameters);
-
             return outputExpressions.ToArray();
         }
     }