Set `jedi:server-args` `safe-local-variable` property to `listp`

Setting the `safe-local-variable` to `listp` allows use of file local variables and directory local variables without the annoying confirmation prompt each time a file is opened.

One possible use case for this is passing the `--virtual-env` argument for each project directory using the `.dir-locals.el` file in the root directory, e.g.

In root project directory `.dir-local.el`:
```lisp
((nil . ((jedi:server-args . ("--virtual-env" "/path/to/venv")))))
```