ices/83737.rs: fixed with no errors

[github-actions]

Issue: rust-lang/rust#83737

#![crate_type = "rlib"]

use core::future::Future;

async fn handle<F>(slf: &F)
where
    F: Fn(&()) -> &mut (dyn Future<Output = ()> + Unpin),
{
    (slf)(&()).await;
}

=== stdout ===
=== stderr ===
warning: function is never used: `handle`
 --> /home/runner/work/glacier/glacier/ices/83737.rs:5:10
  |
5 | async fn handle<F>(slf: &F)
  |          ^^^^^^
  |
  = note: `#[warn(dead_code)]` on by default

warning: 1 warning emitted

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