Should remove `actions.deploy_python_fastapi`

[wch]

The function actions.deploy_python_fastapi is a deprecated code path, and many similar functions were removed in #566. This function was kept because it is used by vetiver here.

At some point, we should:

• Replace actions.deploy_python_fastapi with one that calls the python fastapi deployment code in main.py.
• Update vetiver to call the function from main.py.
• After some time, remove actions.deploy_python_fastapi.