Wrong string for raw block volumes

**This is a...** 
- [ ] Feature Request
- [X] Bug Report

**Problem:**
The documentation says that you should set `volumeMode` to `raw` for a raw block device. In reality you should set it to `block`.

**Proposed Solution:**
Change `raw` to `block`

**Page to Update:**
https://kubernetes.io/docs/concepts/storage/persistent-volumes/#persistent-volumes
