Remove unused extern crate

Author: dvdplm

util/patricia_trie/src/lib.rs

@@ -41,9 +41,6 @@ extern crate keccak_hasher;
 #[cfg(test)]
 extern crate triehash;
 
-#[cfg(test)]
-extern crate env_logger; // TODO: remove
-
 use std::{fmt, error};
 use hashdb::{HashDB, DBValue, Hasher};
 use std::marker::PhantomData;