Revert "Add a shim for #ppx directive for 4.02."

This reverts commit 5cda9ffb99.

The patch was accepted into 4.02 after all:
11bf27a936

src/lib/uTop_main.ml

@@ -85,13 +85,6 @@ let parse_input_multi input =
   in
   (result, Buffer.contents buf)
 
-#if ocaml_version = (4, 02, 0)
-(* #ppx missed the 4.02 merge window. :/ *)
-let () =
-  Hashtbl.add Toploop.directive_table "ppx"
-              (Toploop.Directive_string(fun s -> Clflags.all_ppx := s :: !Clflags.all_ppx))
-#endif
-
 let parse_and_check input eos_is_error =
   let buf = Buffer.create 32 in
   let preprocess input =