fix: remove #![feature(option_result_unwrap_unchecked)]

It's been stabilized by <rust-lang/rust#89951>.

src/r3/src/lib.rs

@@ -13,7 +13,6 @@
 #![feature(exhaustive_patterns)] // `let Ok(()) = Ok::<(), !>(())`
 #![feature(decl_macro)]
 #![feature(set_ptr_value)] // `<*const T>::set_ptr_value`
-#![feature(option_result_unwrap_unchecked)] // `Option<T>::unwrap_unchecked`
 #![feature(cfg_target_has_atomic)] // `#[cfg(target_has_atomic_load_store)]`
 #![feature(never_type)] // `!`
 #![feature(const_type_id)] // `TypeId::of` as `const fn`

src/r3_kernel/src/lib.rs

@@ -1,5 +1,4 @@
 #![feature(const_maybe_uninit_assume_init)]
-#![feature(option_result_unwrap_unchecked)]
 #![feature(const_slice_from_raw_parts)]
 #![feature(const_fn_fn_ptr_basics)]
 #![feature(cfg_target_has_atomic)] // `#[cfg(target_has_atomic_load_store)]`