Fix doctests

Author: oli-obk

library/core/src/intrinsics.rs

@@ -2534,7 +2534,6 @@ extern "rust-intrinsic" {
 /// In other words, the following code has *Undefined Behavior*:
 ///
 /// ```no_run
-/// #![feature(is_val_statically_known)]
 /// #![feature(core_intrinsics)]
 /// # #![allow(internal_features)]
 /// use std::hint::unreachable_unchecked;
@@ -2549,7 +2548,6 @@ extern "rust-intrinsic" {
 /// may panic, or it may not:
 ///
 /// ```no_run
-/// #![feature(is_val_statically_known)]
 /// #![feature(core_intrinsics)]
 /// # #![allow(internal_features)]
 /// use std::intrinsics::is_val_statically_known;