Deprecation warning when using renderPDFPagesToPNG

Hello I'm using the `renderPDFPagesToPNG` and the following depcrecation message appears.
It should be replaced by fs.rm instead.

```
(node:8) [DEP0147] DeprecationWarning: In future versions of Node.js, fs.rmdir(path, { recursive: true }) will be removed. 
Use fs.rm(path, { recursive: true }) instead (Use `node --trace-deprecation ...` to show where the warning was created)
```