ices/99777-3.rs: fixed with errors

[github-actions]

Issue: rust-lang/rust#99777

fn main() {
  match () {
    #[doc(alias = "foo")]
    _ => {}
  }
}

=== stdout ===
=== stderr ===
warning: unused doc comment
 --> /home/runner/work/glacier/glacier/ices/99777-3.rs:3:5
  |
3 |     #[doc(alias = "foo")]
  |     ^^^^^^^^^^^^^^^^^^^^^
4 |     _ => {}
  |     ------- rustdoc does not generate documentation for match arms
  |
  = note: `#[warn(unused_doc_comments)]` on by default
  = help: use `//` for a plain comment

error: `#[doc(alias = "...")]` isn't allowed on match arm
 --> /home/runner/work/glacier/glacier/ices/99777-3.rs:3:11
  |
3 |     #[doc(alias = "foo")]
  |           ^^^^^^^^^^^^^

error: aborting due to previous error; 1 warning emitted

==============