Get User Information doesn't need API key

In this [Get user information docs](https://killbill.github.io/slate/security.html#get-user-information), it stated that calling this API needs:
```
-H "X-Killbill-ApiKey: bob"
-H "X-Killbill-ApiSecret: lazar"
```

During my test, these keys not required, only username:password that is required.