Fixed harmless bug in Day2 code

src/main/kotlin/com/basdado/adventofcode/Day2.kt

@@ -35,7 +35,7 @@ fun puzzle1() {
 fun puzzle2() {
 
     val ids = lines().collect(Collectors.toList())
-    for (i in 0 until ids.size) {
+    for (i in 0 until ids[0].length) {
 
         val shortIds = ids.stream()
             .map { it.substring(0, i) + it.substring(i + 1) }