Remove trait_alias, allow(incomplete_features).

trait_alias seems unused. no idea why it's there.

embassy-traits/src/lib.rs

@@ -2,7 +2,6 @@
 #![feature(generic_associated_types)]
 #![feature(const_fn_fn_ptr_basics)]
 #![feature(const_option)]
-#![allow(incomplete_features)]
 #![feature(type_alias_impl_trait)]
 
 pub mod delay;