unpin litellm version to avoid dependency security issues

[nev-ball]

Currently pyproject.toml pins litellm to 'litellm==1.80.11' This restricts to litellm dependencies with known security issues (e.g. grpcio<1.68.0 with python <3.14). It would be nice to allow latest litellm (e.g. change to 'litellm~=1.80')