fix: Ruff

拒绝不check的邪恶直推！

src/plugins/utils/prompt_builder.py

@@ -3,7 +3,6 @@ import ast
 from typing import Dict, Any, Optional, List, Union
 
 from contextlib import asynccontextmanager
-from typing import Optional, Dict
 import asyncio
 
 class PromptContext: