Update model metadata to set pipeline tag to the new `text-ranking`

Hello!

## Pull Request overview
* Update metadata to set pipeline tag to the new `text-ranking`

## Changes
This is an automated pull request to update the metadata of the model card. We recently introduced the [`text-ranking`](https://huggingface.co/models?pipeline_tag=text-ranking) pipeline tag for models that are used for ranking tasks, and we have a suspicion that this model is one of them.

Feel free to respond if you have questions or concerns.

- Tom Aarsen

README.md

@@ -26,7 +26,7 @@ model_name: rank_zephyr_7b_v1_full-GGUF
 base_model: castorini/rank_zephyr_7b_v1_full
 inference: false
 model_creator: castorini
-pipeline_tag: text-generation
+pipeline_tag: text-ranking
 quantized_by: MaziyarPanahi
 ---
 # [MaziyarPanahi/rank_zephyr_7b_v1_full-GGUF](https://huggingface.co/MaziyarPanahi/rank_zephyr_7b_v1_full-GGUF)