docs: clarify LLM API configuration in mcp_simple_chatbot README (modelcontextprotocol#487)

Co-authored-by: Danny <88821366+ddaltn@users.noreply.github.com>

Author: ddltn

examples/clients/simple-chatbot/README.MD

@@ -25,6 +25,7 @@ This example demonstrates how to integrate the Model Context Protocol (MCP) into
    ```plaintext
    LLM_API_KEY=your_api_key_here
    ```
+   **Note:** The current implementation is configured to use the Groq API endpoint (`https://api.groq.com/openai/v1/chat/completions`) with the `llama-3.2-90b-vision-preview` model. If you plan to use a different LLM provider, you'll need to modify the `LLMClient` class in `main.py` to use the appropriate endpoint URL and model parameters.
 
 3. **Configure servers:**