7.0.0-RC2 - grails.importJavaTime not working

### Expected Behavior

Adding:
```gradle
grails {
    importJavaTime = true
}
```

Should result in default 
```groovy
import java.time.*
```

but results in 
```
unable to resolve class LocalDateTime
```

### Steps To Reproduce

```
git clone --depth 1 --single-branch https://github.com/codeconsole/scaffold-app.git && cd scaffold-app && ./gradlew bootJar
```

### Version

7.0.0-RC2