Docs fix for self-hosted solara instances

[bmorris3]

Description of changes

This is a fix for two bugs in the uvicorn call in the self-hosted docs. The syntax in this call follows the conventions for gunicorn rather than uvicorn, so I've added the host and port flags needed to be specified.

I was also surprised and confused that using one worker caused the server to shutdown when connections were closed. I've changed to workers = 2 in the docs to prevent similar confusion.