Fix TensorFlow Serving links

This tutorial links to /serving, which doesn't exist. I couldn't find a great landing page other than the serving guide, or the GitHub project, so I used the guide. LMK if there's a better choice.

Also added a redirect to catch the external uses.

Reported [here](https://discuss.tensorflow.org/t/broken-link-on-tf-serving/9357)

PiperOrigin-RevId: 446779953

docs/tutorials/serving/rest_simple.ipynb

@@ -67,7 +67,7 @@
         "id": "FbVhjPpzn6BM"
       },
       "source": [
-        "This guide trains a neural network model to classify [images of clothing, like sneakers and shirts](https://github.com/zalandoresearch/fashion-mnist), saves the trained model, and then serves it with [TensorFlow Serving](https://www.tensorflow.org/serving/).  The focus is on TensorFlow Serving, rather than the modeling and training in TensorFlow, so for a complete example which focuses on the modeling and training see the [Basic Classification example](https://github.com/tensorflow/docs/blob/master/site/en/r1/tutorials/keras/basic_classification.ipynb).\n",
+        "This guide trains a neural network model to classify [images of clothing, like sneakers and shirts](https://github.com/zalandoresearch/fashion-mnist), saves the trained model, and then serves it with [TensorFlow Serving](https://www.tensorflow.org/tfx/guide/serving).  The focus is on TensorFlow Serving, rather than the modeling and training in TensorFlow, so for a complete example which focuses on the modeling and training see the [Basic Classification example](https://github.com/tensorflow/docs/blob/master/site/en/r1/tutorials/keras/basic_classification.ipynb).\n",
         "\n",
         "This guide uses [tf.keras](https://github.com/tensorflow/docs/blob/master/site/en/r1/guide/keras.ipynb), a high-level API to build and train models in TensorFlow."
       ]