fix: remove #![feature(const_maybe_uninit_as_ptr)]

`const_maybe_uninit_as_ptr` has been stabilized by
<rust-lang/rust#90896>.

Author: yvt

src/r3_port_arm/src/lib.rs

@@ -2,7 +2,6 @@
 #![feature(const_ptr_offset)]
 #![feature(const_mut_refs)]
 #![feature(const_fn_fn_ptr_basics)]
-#![feature(const_maybe_uninit_as_ptr)]
 #![feature(const_ptr_offset_from)]
 #![feature(const_raw_ptr_deref)]
 #![feature(const_refs_to_cell)]

src/r3_port_arm_m/src/lib.rs

@@ -4,7 +4,6 @@
 #![feature(asm)]
 #![feature(decl_macro)]
 #![feature(generic_const_exprs)]
-#![feature(const_maybe_uninit_as_ptr)]
 #![feature(const_ptr_offset_from)]
 #![feature(const_raw_ptr_deref)]
 #![feature(const_refs_to_cell)]