update branch tag in tutorial (#202)

Author: sixiang-google

README.md

@@ -33,7 +33,7 @@ Follow the steps in
 ## Get the jetstream-pytorch code
 ```bash
 git clone https://github.com/google/jetstream-pytorch.git
-git checkout jetstream-v0.2.3
+git checkout jetstream-v0.2.4
 ```
 
 (optional) Create a virtual env using `venv` or `conda` and activate it.