Auto merge of rust-lang#124836 - tgross35:const-slice-last-chunk, r=BurntSushi

Correct the const stabilization of `last_chunk` for slices

`<[T]>::last_chunk` should have become const stable as part of <rust-lang#117561>. Update the const stability gate to reflect this.

Author: bors

library/core/src/slice/mod.rs

@@ -544,7 +544,7 @@ impl<T> [T] {
     /// ```
     #[inline]
     #[stable(feature = "slice_first_last_chunk", since = "1.77.0")]
-    #[rustc_const_unstable(feature = "const_slice_first_last_chunk", issue = "111774")]
+    #[rustc_const_stable(feature = "slice_first_last_chunk", since = "1.77.0")]
     pub const fn last_chunk<const N: usize>(&self) -> Option<&[T; N]> {
         if self.len() < N {
             None