Fix gradio-client.mdx

Author: burtenshaw

units/en/unit2/gradio-client.mdx

@@ -94,10 +94,6 @@ try:
     model = InferenceClientModel()
     agent = CodeAgent(tools=[*tools], model=model)
 
-    def call_agent(message, history):
-        return str(agent.run(message))
-
-
     demo = gr.ChatInterface(
         fn=lambda message, history: str(agent.run(message)),
         type="messages",