Super-parameters de-sugaring example contains super-parameters

https://github.com/dart-lang/language/blob/master/working/1855%20-%20super%20parameters/proposal.md#examples

```dart
class C extends B {
C(super.foo, super.bar, [super.baz = 4]);
// Same as:
// C(super.foo, super.bar, [super.baz = 4]) : super(foo, bar, baz);
}
```

Unless I'm misunderstanding what the example is indicating... I think the comment should not contain super-parameters.

Open working/1855 - super parameters/proposal.md at the Examples section and compare the shorthand constructor with its desugared form. Update the commented equivalent so it no longer uses super-parameters, then verify that the example accurately represents the intended transformation.

Written by the indexing model from the issue text.