Update llm.py to use litellm.support_function_calling()

[Notnaton]

Using litellm.supports_function_calling to check if model supports function calling if function calling is not specified.

Describe the changes you have made:

Reference any relevant issues (e.g. "Fixes #000"):

Pre-Submission Checklist (optional but appreciated):

• [ ] I have included relevant documentation updates (stored in /docs)
• [ ] I have read docs/CONTRIBUTING.md
• [ ] I have read docs/ROADMAP.md

OS Tests (optional but appreciated):

• [ ] Tested on Windows
• [ ] Tested on MacOS
• [ ] Tested on Linux