fix clippy (#321)

authority/src/default_weight.rs

@@ -6,6 +6,7 @@
 
 #![allow(unused_parens)]
 #![allow(unused_imports)]
+#![allow(clippy::unnecessary_cast)]
 
 use frame_support::weights::{constants::RocksDbWeight as DbWeight, Weight};
 use sp_std::marker::PhantomData;