fix script in README

Author: jpn--

README.md

@@ -28,11 +28,23 @@ for the `prototype_mtc_extended` example model.
 
 ```python
 from pathlib import Path
-from activitysim.examples.external import registered_external_example
-
-example_dir = registered_external_example(
-    name="prototype_mtc_extended", 
-    working_dir=Path.cwd()
+from activitysim.examples.external import download_external_example
+
+example_dir = download_external_example(
+  name="prototype_mtc_extended", 
+  working_dir=Path.cwd(),
+  url="https://github.com/ActivitySim/activitysim-prototype-mtc/archive/refs/heads/extended.tar.gz",
+  assets={
+    "data_full.tar.zst": {
+      "url": "https://github.com/ActivitySim/activitysim-prototype-mtc/releases/download/v1.3.4/data_full.tar.zst",
+      "sha256": "b402506a61055e2d38621416dd9a5c7e3cf7517c0a9ae5869f6d760c03284ef3",
+      "unpack": "data_full",
+    },
+    "test/prototype_mtc_reference_pipeline.zip": {
+      "url": "https://github.com/ActivitySim/activitysim-prototype-mtc/releases/download/v1.3.2/prototype_mtc_extended_reference_pipeline.zip",
+      "sha256": "4d94b6a8a83225dda17e9ca19c9110bc1df2df5b4b362effa153d1c8d31524f5",
+    }
+  }
 )
 ```
 
@@ -42,5 +54,6 @@ The `prototype_mtc` example model is run using the `activitysim` command line to
 A quick and easy way to run the model for benchmarking is to use the following command:
 
 ```shell
+cd activitysim-prototype-mtc-extended
 activitysim workflow performance-benchmarking
 ```