Refactor _process_reasoning_stream to remove 'self'

Removed 'self' parameter from _process_reasoning_stream function.

Author: flyinglandlord

lightllm/server/api_openai.py

@@ -125,7 +125,6 @@ def _get_reasoning_from_request(request: ChatCompletionRequest) -> bool:
 
 
 def _process_reasoning_stream(
-    self,
     index: int,
     delta: str,
     reasoning_parser_dict: Dict[int, ReasoningParser],