`Add final initializing formal parameters` quick-fix false-negative on enums

[FMorschel]

Repro:

class A {
  A(); // Quick-fix shows
  final int v;
}

enum E {
  a;
  const E(); // Nothing
  final int v;
}

[FMorschel]

Here is the CL for this https://dart-review.googlesource.com/c/sdk/+/457400