Fix unused import warning in test_utils

Author: tnull

lightning/src/util/test_utils.rs

@@ -62,7 +62,6 @@ use regex;
 use crate::io;
 use crate::prelude::*;
 use core::cell::RefCell;
-use core::ops::Deref;
 use core::time::Duration;
 use crate::sync::{Mutex, Arc};
 use core::sync::atomic::{AtomicBool, AtomicUsize, Ordering};