Revert "fix ci warning"

This reverts commit 81bc367.

Author: liamkinne

embedded-can/src/lib.rs

@@ -2,12 +2,6 @@
 
 #![warn(missing_docs)]
 #![no_std]
-// disable warning for already-stabilized features.
-// Needed to pass CI, because we deny warnings.
-// We don't immediately remove them to not immediately break older nightlies.
-// When all features are stable, we'll remove them.
-#![cfg_attr(nightly, allow(stable_features, unknown_lints))]
-#![cfg_attr(nightly, feature(async_fn_in_trait, impl_trait_projections))]
 #![allow(async_fn_in_trait)]
 
 pub mod asynch;