Fix unused import build warning

Author: jkczyz

lightning/src/util/wakers.rs

@@ -27,8 +27,6 @@ use core::future::Future as StdFuture;
 use core::task::{Context, Poll};
 use core::pin::Pin;
 
-use prelude::*;
-
 /// Used to signal to one of many waiters that the condition they're waiting on has happened.
 pub(crate) struct Notifier {
 	notify_pending: Mutex<(bool, Option<Arc<Mutex<FutureState>>>)>,