Get rid of rustc_hex in favor of hex (#5370)

* Get rid of rustc_hex in favor of hex

* Use HexDisplay

substrate/bin/node/runtime/src/lib.rs

@@ -68,7 +68,6 @@ use impls::{CurrencyToVoteHandler, Author, LinearWeightToFee, TargetedFeeAdjustm
 /// Constant values used within the runtime.
 pub mod constants;
 use constants::{time::*, currency::*};
-use frame_system::Trait;
 
 // Make the WASM binary available.
 #[cfg(feature = "std")]