Aura: Remove unused structures and adds SlotDuration::get() (#1565)

substrate/node/runtime/src/lib.rs

@@ -80,7 +80,6 @@ use council::seats as council_seats;
 #[cfg(any(feature = "std", test))]
 use version::NativeVersion;
 use substrate_primitives::OpaqueMetadata;
-use consensus_aura::api as aura_api;
 
 #[cfg(any(feature = "std", test))]
 pub use runtime_primitives::BuildStorage;
@@ -335,7 +334,7 @@ impl_runtime_apis! {
 		}
 	}
 
-	impl aura_api::AuraApi<Block> for Runtime {
+	impl consensus_aura::AuraApi<Block> for Runtime {
 		fn slot_duration() -> u64 {
 			Aura::slot_duration()
 		}