It's Clippy time (#3806)

Fix some Clippy issues

substrate/srml/support/src/hash.rs

@@ -59,7 +59,7 @@ impl StorageHasher for Twox64Concat {
 	type Output = Vec<u8>;
 	fn hash(x: &[u8]) -> Vec<u8> {
 		twox_64(x)
-			.into_iter()
+			.iter()
 			.chain(x.into_iter())
 			.cloned()
 			.collect::<Vec<_>>()

substrate/srml/support/src/traits.rs

@@ -148,7 +148,7 @@ pub trait OnUnbalanced<Imbalance> {
 	fn on_unbalanced(amount: Imbalance);
 }
 
-impl<Imbalance: Drop> OnUnbalanced<Imbalance> for () {
+impl<Imbalance> OnUnbalanced<Imbalance> for () {
 	fn on_unbalanced(amount: Imbalance) { drop(amount); }
 }