rm const_err lint

Author: japaric

src/lib.rs

@@ -78,7 +78,6 @@
 #![deny(rust_2018_compatibility)]
 #![deny(rust_2018_idioms)]
 #![deny(warnings)]
-#![deny(const_err)]
 
 pub use binary_heap::BinaryHeap;
 pub use deque::Deque;