get rid of executable

expect tests will make them kinda pointless

exe/dune

@@ -1,4 +0,0 @@
-(executable
- (public_name aoc)
- (name main)
- (libraries aoc))

exe/main.ml

@@ -1,15 +0,0 @@
-open Aoc
-
-let () =
-  Day1.print ();
-  Day2.print ();
-  Day3.print ();
-  Day4.print ();
-  Day5.print ();
-  Day6.print ();
-  Day7.print ();
-  Day8.print ();
-  Day9.print ();
-  Day10.print ();
-  Day11.print ()
-;;