db.updateUser and db.replaceUser using wrong urls

The functions `updateUser` and `replaceUser` in the `database.ts` file ([here](https://github.com/arangodb/arangojs/blob/main/src/database.ts)) seems to point towards wrong urls: 

```
...
        path: `/api/user/${encodeURIComponent(username)}`,
...
```
instead of:
```
...
        path: `/_api/user/${encodeURIComponent(username)}`,
...
```
(note the underscore in `/_api`)