fix re sub bug (#2199)

### What problem does this PR solve?



### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

rag/llm/tts_model.py

@@ -53,9 +53,10 @@ class Base(ABC):
     def tts(self, audio):
         pass
     
-    def normalize_text(text):
+    def normalize_text(self, text):
         return re.sub(r'(\*\*|##\d+\$\$|#)', '', text)
 
+
 class FishAudioTTS(Base):
     def __init__(self, key, model_name, base_url="https://api.fish.audio/v1/tts"):
         if not base_url: