update bootstrap configs

library/core/src/array/mod.rs

@@ -147,7 +147,6 @@ pub const fn from_ref<T>(s: &T) -> &[T; 1] {
 /// Converts a mutable reference to `T` into a mutable reference to an array of length 1 (without copying).
 #[stable(feature = "array_from_ref", since = "1.53.0")]
 #[rustc_const_stable(feature = "const_array_from_ref", since = "1.83.0")]
-#[cfg_attr(bootstrap, rustc_allow_const_fn_unstable(const_mut_refs))]
 pub const fn from_mut<T>(s: &mut T) -> &mut [T; 1] {
     // SAFETY: Converting `&mut T` to `&mut [T; 1]` is sound.
     unsafe { &mut *(s as *mut T).cast::<[T; 1]>() }