The following warning was happening in CI:

```
(node:11982) [DEP0147] DeprecationWarning: In future versions of Node.js, fs.rmdir(path, { recursive: true }) will be removed. Use fs.rm(path, { recursive: true }) instead
```

Simply replaces the `rmdir` with `rm`. Note that the `sync` methods
are used here instead of the async promise based methods.