Remove old documentation about the timer::CountDown trait

Author: GrantM11235

src/delay.rs

@@ -1,11 +1,4 @@
 //! Delays
-//!
-//! # What's the difference between these traits and the `timer::CountDown` trait?
-//!
-//! The `Timer` trait provides a *non-blocking* timer abstraction and it's meant to be used to build
-//! higher level abstractions like I/O operations with timeouts. OTOH, these delays traits only
-//! provide *blocking* functionality. Note that you can also use the `timer::CountDown` trait to
-//! implement blocking delays.
 
 /// Blocking delay traits
 pub mod blocking {