ices/84789.rs: fixed with errors

[github-actions]

Issue: rust-lang/rust#84789

#![feature(trait_alias)]

pub trait MyFn = Fn(&mut Self);

// 1.
pub type F = dyn MyFn;

// 2.
pub fn f(_f: &dyn MyFn) {
    
}

fn main() {}

=== stdout ===
=== stderr ===
error[E0038]: the trait alias `MyFn` cannot be made into an object
 --> /home/runner/work/glacier/glacier/ices/84789.rs:6:18
  |
6 | pub type F = dyn MyFn;
  |                  ^^^^
  |
  = note: it cannot use `Self` as a type parameter in a supertrait or `where`-clause

error[E0038]: the trait alias `MyFn` cannot be made into an object
 --> /home/runner/work/glacier/glacier/ices/84789.rs:9:19
  |
9 | pub fn f(_f: &dyn MyFn) {
  |                   ^^^^
  |
  = note: it cannot use `Self` as a type parameter in a supertrait or `where`-clause

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0038`.
==============