GRAILS-11309 hasErrors documentation: it.defaultMessage is probably not the best example

http://grails.org/doc/latest/ref/Tags/hasErrors.html

using it.defaultMessage with a custom validator produces a message like:

Property [{0}] of class [{1}] with value [{2}] does not pass custom validation

Seems like a better example would use g:message which actually resolves the code:

```
<g:message error="${it}"/>
```