Remove unused core_intrinsics feature gate

src/main.rs

@@ -42,8 +42,6 @@
 // Ensure that all must_use results are used
 #![deny(unused_must_use)]
 #![feature(allocator_api)]
-#![feature(core_intrinsics)]
-#![allow(internal_features)]
 #![feature(int_roundings)]
 #![feature(iter_next_chunk)]
 #![feature(let_chains)]