cleanup: Remove unused braces in use statements

src/liballoc/arc.rs

@@ -76,7 +76,7 @@ use core::prelude::*;
 use core::atomic;
 use core::atomic::Ordering::{Relaxed, Release, Acquire, SeqCst};
 use core::fmt;
-use core::cmp::{Ordering};
+use core::cmp::Ordering;
 use core::default::Default;
 use core::mem::{min_align_of, size_of};
 use core::mem;