ices/58987-3.rs: fixed with no errors

=== stdout ===
=== stderr ===
warning: the feature `const_generics` is incomplete and may cause the compiler to crash
 --> /home/runner/work/glacier/glacier/ices/58987-3.rs:1:12
  |
1 | #![feature(const_generics)]
  |            ^^^^^^^^^^^^^^
  |
  = note: `#[warn(incomplete_features)]` on by default

warning: struct is never constructed: `NibblePack`
 --> /home/runner/work/glacier/glacier/ices/58987-3.rs:3:8
  |
3 | struct NibblePack<const N: usize> ([u8; N / 1]);
  |        ^^^^^^^^^^
  |
  = note: `#[warn(dead_code)]` on by default

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

Author: rustbot