remove redundant use declarations

Author: marcelbuesing

tests/smoke.rs

@@ -2,7 +2,6 @@ use std::error::Error;
 use std::pin::Pin;
 use std::time::{Duration, Instant};
 
-use async_std;
 use futures_timer::Delay;
 
 #[async_std::test]

tests/timeout.rs

@@ -1,7 +1,6 @@
 use std::error::Error;
 use std::time::{Duration, Instant};
 
-use async_std;
 use futures_timer::Delay;
 
 #[async_std::test]