Add manual transformers dep override instructions

Author: jackzhxng

examples/models/voxtral/README.md

@@ -9,6 +9,9 @@ To export the model, we use [Optimum ExecuTorch](https://github.com/huggingface/
 Install through pip package:
 ```
 pip install optimum-excecutorch
+
+# We are currently working on a Transformers pin bump for Optimum. In the meantime, manually override the Transformers dep.
+pip install git+https://github.com/huggingface/transformers@6121e9e46c4fc4e5c91d9f927aef5490691850cf#egg=transformers
 ```
 
 Or install from source: