An error in Colab: Tutorial: Rectified Flow with Neural Network.ipynb

When training rectified_flow_2,  the code `rectified_flow_2.net = copy.deepcopy(rectified_flow_1)` is wrong and  useless. In fact, I think you should use `rectified_flow_2.model.load_state_dict(rectified_flow_1.model.state_dict())` to load pretrained parameters of rectified_flow_1.