Tag model as `transformers` instead of `keras`

This repo doesn't look like a Keras 3.0 model. This PR updates the model card metadata to make sure the model repo is correctly referenced as a `transformers` repo. This is useful for discoverability on the search page + for the `"Use this model"` code snippet.

If this repo is indeed compatible with Keras, it would still be good to add `transformers` as a tag + explain in the readme how to load the model with Keras. I can work on that if relevant.

Cheers! 🤗

README.md

@@ -2,7 +2,7 @@
 license: mit
 language:
 - en
-library_name: keras
+library_name: transformers
 ---
 # Model Card for Model ID