local-grid: Use upstream `vagrant-guest.nix`.

It looks like this may have been originally copied from a newer nixpkgs
since it wasn't in our nixpkgs fork.

The differences I can see:
- Details of `sudoer` file, some of which appear to be duplicates.
- `jq` and `gnumake` are not on the system path
- `vagrant` user is in group `users` instead of `vagrant`.