f clarify comment

Author: TheBlueMatt

lightning/src/routing/router.rs

@@ -1652,7 +1652,7 @@ where L::Target: Logger {
 
 	// First, sort by the cost-per-value of the path, dropping the paths which cost the most for
 	// the value they contribute towards the payment amount.
-	// We sort backwards as we will remove from the front in `retain`, next.
+	// We sort in descending order as we will remove from the front in `retain`, next.
 	selected_route.sort_unstable_by(|a, b|
 		(((b.get_cost_msat() as u128) << 64) / (b.get_value_msat() as u128))
 			.cmp(&(((a.get_cost_msat() as u128) << 64) / (a.get_value_msat() as u128)))