delete super.name shouldn't work

Flow version: master

```js
class Bar {
name: string | void
}

class Foo extends Bar {
bar() {
delete super.name;
}
}
```
## Expected behavior

```
^ Cannot delete `super.name` [1] because only member expressions and variables can be deleted.
```

## Actual behavior

```
No errors
```

* Link to Try-Flow or Github repo: