Remove tfs_z

See https://github.com/ollama/ollama/blob/main/docs/api.md#request-8

tfs_z was removed from Llama.cpp and Ollama in January 2025.

backend/open_webui/utils/payload.py

@@ -78,7 +78,6 @@ def apply_model_params_to_body_ollama(params: dict, form_data: dict) -> dict:
         "num_keep",
         "num_predict",
         "repeat_last_n",
-        "tfs_z",
         "top_k",
         "min_p",
         "typical_p",