[bugfix] fix response_prefix (#7126)

Author: Jintao-Huang

swift/llm/infer/infer_engine/sglang_engine.py

@@ -146,8 +146,6 @@ def _create_chat_completion_response(self, output, inputs, template, return_deta
         meta_info = output['meta_info']
         usage_info = self._get_usage_info(meta_info['prompt_tokens'], meta_info['completion_tokens'])
         response = template.decode(output['output_ids'])
-        if template.template_meta.response_prefix:
-            response = template.template_meta.response_prefix + response
         toolcall = self._get_toolcall(response, template)
         token_ids = output['output_ids'] if return_details else None
         choice = ChatCompletionResponseChoice(