Fix custom test case for day 9

src/day9.rs

@@ -167,5 +167,5 @@ fn test_part2() {
 #[test]
 fn test_part2_bonus() {
     let mut day = Day9::create("2931514".to_string());
-    assert_eq!("180", day.solve_part2());
+    assert_eq!("158", day.solve_part2());
 }