fix bug

test.py

@@ -18,7 +18,7 @@ rag = LightRAG(
     # llm_model_func=gpt_4o_complete  # Optionally, use a stronger model
 )
 
-with open("./book.txt") as f:
+with open("./dickens/book.txt", "r", encoding="utf-8") as f:
     rag.insert(f.read())
 
 # Perform naive search