refactor: remove unused cfg_attr statement (#15)

Author: wmmc88

general/echo/kmdf/exe/src/main.rs

@@ -8,7 +8,6 @@
 //! Idiomatic Rust wrappers for the Windows Driver Kit (WDK) APIs. This crate is
 //! built on top of the raw FFI bindings provided by [`wdk-sys`], and provides a
 //! safe, idiomatic rust interface to the WDK.
-#![cfg_attr(feature = "nightly", feature(hint_must_use))]
 #![deny(missing_docs)]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![deny(clippy::all)]