day23 part 2 (with a shortcut that could potentially break some cases)

I'm only using a lower bound on the number of intersections a cube has.

src/main.rs

@@ -1,4 +1,4 @@
 fn main() {
-    aoc_2018::tasks::day24::task1();
-    // aoc_2018::tasks::day23::task2();
+    // aoc_2018::tasks::day24::task1();
+    aoc_2018::tasks::day23::task2();
 }