Update broken link for Frozen Model hyperlink in README.md (#8063)

Co-authored-by: Ping Yu <[email protected]>

tfjs-converter/README.md

@@ -186,7 +186,7 @@ most cases.
 | `keras_saved_model` | `tfjs_layers_model` | Convert a tf.keras SavedModel model file (from [`tf.contrib.saved_model.save_keras_model`](https://www.tensorflow.org/api_docs/python/tf/contrib/saved_model/save_keras_model)) to TensorFlow.js Layers model format. Use [`tf.loadLayersModel()`](https://js.tensorflow.org/api/latest/#loadLayersModel) to load the model in JavaScript. |
 | `tf_hub` | `tfjs_graph_model` | Convert a [TF-Hub](https://www.tensorflow.org/hub) model file to TensorFlow.js graph model format. Use [`tf.loadGraphModel()`](https://js.tensorflow.org/api/latest/#loadGraphModel) to load the converted model in JavaScript. |
 | `tf_saved_model` | `tfjs_graph_model` | Convert a [TensorFlow SavedModel](https://www.tensorflow.org/guide/saved_model#build_and_load_a_savedmodel) to TensorFlow.js graph model format. Use [`tf.loadGraphModel()`](https://js.tensorflow.org/api/latest/#loadGraphModel) to load the converted model in JavaScript. |
-| `tf_frozen_model` | `tfjs_graph_model` | Convert a [Frozen Model](https://www.tensorflow.org/mobile/prepare_models#how_do_you_get_a_model_you_can_use_on_mobile) to TensorFlow.js graph model format. Use [`tf.loadGraphModel()`](https://js.tensorflow.org/api/latest/#loadGraphModel) to load the converted model in JavaScript. |
+| `tf_frozen_model` | `tfjs_graph_model` | Convert a [Frozen Model](https://medium.com/@sebastingarcaacosta/how-to-export-a-tensorflow-2-x-keras-model-to-a-frozen-and-optimized-graph-39740846d9eb) to TensorFlow.js graph model format. Use [`tf.loadGraphModel()`](https://js.tensorflow.org/api/latest/#loadGraphModel) to load the converted model in JavaScript. |
 
 #### JavaScript-to-Python