Fix the link to diffusion_1d_resample.py (#1702)

Author: vl-dud

deepxde/model.py

@@ -589,7 +589,7 @@ def train(
                 - If you solve PDEs via ``dde.data.PDE`` or ``dde.data.TimePDE``, do not use `batch_size`, and instead use
                   `dde.callbacks.PDEPointResampler
                   <https://deepxde.readthedocs.io/en/latest/modules/deepxde.html#deepxde.callbacks.PDEPointResampler>`_,
-                  see an `example <https://github.com/lululxvi/deepxde/blob/master/examples/diffusion_1d_resample.py>`_.
+                  see an `example <https://github.com/lululxvi/deepxde/blob/master/examples/pinn_forward/diffusion_1d_resample.py>`_.
                 - For DeepONet in the format of Cartesian product, if `batch_size` is an Integer,
                   then it is the batch size for the branch input; if you want to also use mini-batch for the trunk net input,
                   set `batch_size` as a tuple, where the fist number is the batch size for the branch net input