[doc] Issue in "Downstream cluster image definition file" - sshKeys require home dir creation

Downstream cluster image definition file:

https://documentation.suse.com/suse-edge/3.3/html/edge/quickstart-metal3.html#id-downstream-cluster-image-definition-file

```
  sshKeys:
  - $USERKEY1"
```

Requires 
  `createHomeDir: true`

Multiple occurrences within the documentation.