Remove unused uses.

src/liballoc/tests/binary_heap.rs

@@ -1,11 +1,7 @@
 use std::collections::BinaryHeap;
 use std::collections::binary_heap::{Drain, PeekMut};
-use std::panic::{self, AssertUnwindSafe};
-use std::sync::atomic::{AtomicUsize, Ordering};
 use std::iter::TrustedLen;
 
-use rand::{thread_rng, seq::SliceRandom};
-
 #[test]
 fn test_iterator() {
     let data = vec![5, 9, 3];