Update the library name, so this repository is correctly detected as an MLX model

This allows apps that support the MLX format to list this repository for download.

LM Studio, for example, is currently not listing this repository, as you can see [here](https://huggingface.co/models?apps=lmstudio), so users are not able to download it from its built-in model manager.

README.md

@@ -1,5 +1,5 @@
 ---
-library_name: transformers
+library_name: mlx
 license: apache-2.0
 license_link: https://huggingface.co/Qwen/Qwen3-14B/blob/main/LICENSE
 pipeline_tag: text-generation