[cfe] Should not report a compile-time error on final super parameter

[eernstg]

Cf. #48699. Consider the following program:

class Base {
  int value;
  Base(this.value);
}

class Extended extends Base {
  Extended(final super.value);
}

This program gives rise to a compile-time error with the current CFE, commit ac19f52:

n028.dart:7:5: Error: Can't have modifier 'final' here.
Try removing 'final'.
  B(final super.x);
    ^^^^^

However, I cannot find any rules against having the modifier final on a super parameter. It is final already, but it should be benign to specify it explicitly as well.

The behavior seems to have been introduced quite recently, it does not occur with a dart from 2.17.0-212.0.dev.