ices/100689.rs: fixed with no errors

=== stdout ===
=== stderr ===
warning: the feature `generic_associated_types` has been stable since 1.65.0 and no longer requires an attribute to enable
 --> /home/runner/work/glacier/glacier/ices/100689.rs:1:12
  |
1 | #![feature(generic_associated_types)]
  |            ^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: `#[warn(stable_features)]` on by default

warning: field `foo` is never read
 --> /home/runner/work/glacier/glacier/ices/100689.rs:4:5
  |
3 | struct Foo<'a> {
  |        --- field in this struct
4 |     foo: &'a mut usize,
  |     ^^^
  |
  = note: `#[warn(dead_code)]` on by default

warning: 2 warnings emitted

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

Author: rustbot