Fix non-supported argument

app.py

@@ -139,7 +139,6 @@ model = HfApiModel(
 max_tokens=2096,
 temperature=0.5,
 model_id='Qwen/Qwen2.5-Coder-32B-Instruct',# it is possible that this model may be overloaded
-fallback_model_id='meta-llama/Meta-Llama-3-70B-Instruct',  # Fallback model
 custom_role_conversions=None,
 )