Fix transaction payment runtime api (#6792)

The transaction payment runtime api used its own extrinsic generic
parameter. This is wrong, because this resulted in using always the
native extrinsic. If there was a runtime upgrade that changed the
extrinsic in some way, it would result in the api breaking. The correct
way is to use the `Extrinsic` from the `Block` parameter. This is on the
node side the opaque extrinsic and on the runtime side the real extrinsic.

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

@@ -1101,9 +1101,8 @@ impl_runtime_apis! {
 	impl pallet_transaction_payment_rpc_runtime_api::TransactionPaymentApi<
 		Block,
 		Balance,
-		UncheckedExtrinsic,
 	> for Runtime {
-		fn query_info(uxt: UncheckedExtrinsic, len: u32) -> RuntimeDispatchInfo<Balance> {
+		fn query_info(uxt: <Block as BlockT>::Extrinsic, len: u32) -> RuntimeDispatchInfo<Balance> {
 			TransactionPayment::query_info(uxt, len)
 		}
 	}