remove unneeded import

Author: rapha

src/libstd/sync/mpsc/mod.rs

@@ -277,7 +277,6 @@ pub use self::select::{Select, Handle};
 use self::select::StartResult;
 use self::select::StartResult::*;
 use self::blocking::SignalToken;
-use iter::IntoIterator;
 
 mod blocking;
 mod oneshot;