update the comment in day 15.1

src/day15.ml

@@ -88,8 +88,8 @@ let%expect_test "Day 15.1" =
     |> Iter.sort_uniq ~cmp:Int.compare
   in
   (* iterate thru the intersections by ascending x.
-     if a point in the region can be a beacon,
-     then every point in the region is. *)
+     if a point in the region between two intersections can be a beacon,
+     then every point in the region can be. *)
   let rec count_not_beacons count xs =
     match xs with
     | lx :: hx :: rest ->