Rollup merge of #81590 - KodrAus:stabilize/int_bits_const, r=m-ou-se

Stabilize int_bits_const

Closes #76904

The FCP to stabilize the `int_bits_const` feature completed on the tracking issue.

compiler/rustc_data_structures/src/lib.rs

@@ -13,7 +13,6 @@
 #![feature(unboxed_closures)]
 #![feature(generator_trait)]
 #![feature(fn_traits)]
-#![feature(int_bits_const)]
 #![feature(min_specialization)]
 #![feature(auto_traits)]
 #![feature(nll)]

compiler/rustc_serialize/src/lib.rs

@@ -17,7 +17,6 @@ Core encoding and decoding interfaces.
 #![feature(min_specialization)]
 #![feature(vec_spare_capacity)]
 #![feature(core_intrinsics)]
-#![feature(int_bits_const)]
 #![feature(maybe_uninit_slice)]
 #![feature(new_uninit)]
 #![cfg_attr(test, feature(test))]

compiler/rustc_serialize/tests/leb128.rs

@@ -1,4 +1,3 @@
-#![feature(int_bits_const)]
 #![feature(maybe_uninit_slice)]
 #![feature(maybe_uninit_uninit_array)]