Polish model card overview and usage notes

README.md

@@ -27,7 +27,7 @@ from this repository's metadata and artifacts.
 |---|---|
 | Format | **Transformers** |
 | Source / base | [`google/gemma-4-31B-it`](https://huggingface.co/google/gemma-4-31B-it) |
-| Intended task | `text-generation` |
+| Intended task | `image-text-to-text` |
 | License | `gemma` |
 
 ## What is included