Add trust_remote_code parameter and remove True

- Introduced a new model parameter `trust_remote_code`
- Set the default value of `trust_remote_code` to `False`
  to enhance security


Former-commit-id: 4bf23f406cf5235c16f9f8139850c53354901814

src/llamafactory/model/model_utils/unsloth.py

@@ -39,7 +39,7 @@ def _get_unsloth_kwargs(
         "device_map": {"": get_current_device()},
         "rope_scaling": getattr(config, "rope_scaling", None),
         "fix_tokenizer": False,
-        "trust_remote_code": True,
+        "trust_remote_code": model_args.trust_remote_code,
         "use_gradient_checkpointing": "unsloth",
     }