gen_js_api 1.1.* tests are not compatible with latest js_of_ocaml

[mseri]

Fails with

 -let (_ : string of_js) = Ojs.string_of_js
 -let (_ : string to_js) = Ojs.string_to_js
 -let (_ : int of_js) = Ojs.int_of_js
 -let (_ : int to_js) = Ojs.int_to_js
 -let (_ : bool of_js) = Ojs.bool_of_js
 -let (_ : bool to_js) = Ojs.bool_to_js
 -let (_ : float of_js) = Ojs.float_of_js
 -let (_ : float to_js) = Ojs.float_to_js
 -let (_ : Ojs.t of_js) = fun (x9 : Ojs.t) -> x9
 -let (_ : Ojs.t to_js) = fun (x10 : Ojs.t) -> x10
 -let (_ : (string * int) of_js) =
 +let _ = Ojs.string_of_js
 +let _ = Ojs.string_to_js
 +let _ = Ojs.int_of_js
 +let _ = Ojs.int_to_js
 +let _ = Ojs.bool_of_js
 +let _ = Ojs.bool_to_js
 +let _ = Ojs.float_of_js
 +let _ = Ojs.float_to_js
 +let _ = fun (x9 : Ojs.t) -> x9
 +let _ = fun (x10 : Ojs.t) -> x10
 +let _ =
    fun (x11 : Ojs.t) ->
      let x12 = x11 in
      ((Ojs.string_of_js (Ojs.array_get x12 0)),
        (Ojs.int_of_js (Ojs.array_get x12 1)))
 -let (_ : (string * int) to_js) =
 +let _ =
    fun (x13 : (string * int)) ->
      let (x14, x15) = x13 in
      let x16 = Ojs.array_make 2 in
      Ojs.array_set x16 0 (Ojs.string_to_js x14);
      Ojs.array_set x16 1 (Ojs.int_to_js x15);
      x16

[mseri]

Seen on #28144

[raphael-proust]

Thanks!