Update Js_of_ocaml upper bounds in preparation to release 6.0.0

[vouillon]

We are making more breaking API changes (ocsigen/js_of_ocaml#1769). Below are some errors this produces.

https://opam.ci.ocaml.org/github/ocaml/opam-repository/commit/22026917fe3999cd41b20dc51481253aab1fa1c5/variant/compilers,4.14,js_of_ocaml-compiler.6.0.0,revdeps,async_js.v0.15.1

# File "src/http.ml", line 142, characters 14-26:
# 142 |   Optdef.iter req##.upload (fun upload ->
#                     ^^^^^^^^^^^^
# Error: This expression has type
#          Js_of_ocaml.XmlHttpRequest.xmlHttpRequestUpload Js_of_ocaml__.Js.t =
#            Js_of_ocaml.XmlHttpRequest.xmlHttpRequestUpload Js_of_ocaml.Js.t
#        but an expression was expected of type
#          'a Optdef.t = 'a Js_of_ocaml.Js.optdef

https://opam.ci.ocaml.org/github/ocaml/opam-repository/commit/22026917fe3999cd41b20dc51481253aab1fa1c5/variant/compilers,4.14,js_of_ocaml-compiler.6.0.0,revdeps,ezjs_extension.0.1

# File "src/local/storage_local.ml", line 4, characters 25-55:
# 4 |   match Optdef.to_option Dom_html.window##.localStorage with
#                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
# Error: This expression has type
#          Ezjs_min.Dom_html.storage Js_of_ocaml__.Js.t =
#            Ezjs_min.Dom_html.storage Js_of_ocaml.Js.t
#        but an expression was expected of type
#          'a Ezjs_min.Optdef.t = 'a Js_of_ocaml.Js.optdef

https://opam.ci.ocaml.org/github/ocaml/opam-repository/commit/22026917fe3999cd41b20dc51481253aab1fa1c5/variant/compilers,4.14,js_of_ocaml-compiler.6.0.0,revdeps,jsoo_storage.1.0.1

# File "src/webStorage.ml", line 261, characters 15-77:
# 261 | module Local = Make (struct let handler = Dom_html.window##.localStorage end)
#                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
# Error: Modules do not match:
#        sig val handler : Js_of_ocaml.Dom_html.storage Js_of_ocaml__.Js.t end
#      is not included in sig val handler : t Js_of_ocaml.Js.optdef end
#      Values do not match:
#        val handler : Js_of_ocaml.Dom_html.storage Js_of_ocaml__.Js.t
#      is not included in
#        val handler : t Js_of_ocaml.Js.optdef
#      The type
#        Js_of_ocaml.Dom_html.storage Js_of_ocaml__.Js.t =
#          Js_of_ocaml.Dom_html.storage Js_of_ocaml.Js.t
#      is not compatible with the type t Js_of_ocaml.Js.optdef
#      File "src/webStorage.ml", line 102, characters 21-46:
#        Expected declaration
#      File "src/webStorage.ml", line 261, characters 32-39: Actual declaration

https://opam.ci.ocaml.org/github/ocaml/opam-repository/commit/22026917fe3999cd41b20dc51481253aab1fa1c5/variant/compilers,4.14,js_of_ocaml-compiler.6.0.0,revdeps,virtual_dom.v0.16.0

# File "src/attr.ml", line 513, characters 23-37:
# 513 |         Js.Optdef.case target##.files const_ignore (fun files -> handler ev files))))
#                              ^^^^^^^^^^^^^^
# Error: This expression has type
#          Js_of_ocaml__.File.fileList Js_of_ocaml__.Js.t =
#            Js_of_ocaml__.File.fileList Js_of_ocaml.Js.t
#        but an expression was expected of type
#          'a Js_of_ocaml.Js.Optdef.t = 'a Js_of_ocaml.Js.optdef

[mseri]

Thanks