fix: set uvicorn worker to 1

[ccheng26]

Changes

change amount of worker #'s to 1

Context for reviewers

Chainlit uses Socket.io for backend server connections; multiple workeres are currently unsupported by gunicorn
https://flask-socketio.readthedocs.io/en/latest/deployment.html#gunicorn-web-server

Testing

Run make start
Navigate to localhost:8000/chat and enter a query into the chatbot, response should be returned

[yoomlam]

Also revert docker-compose to use uvicorn so that hot-loading is restored