Note that immutable arrays and labeled tuples will be in OCaml 5.4 (#4009)

* Note that immutable arrays and labeled tuples will be in OCaml 5.4

* Update jane/doc/extensions/_08-miscellaneous-extensions/labeled-tuples.md

Author: avsm

jane/doc/extensions/_08-miscellaneous-extensions/immutable-arrays.md

@@ -34,3 +34,5 @@ type `super`, then `sub iarray` is a subtype of `super iarray`, as though you ha
 
 You can also have *immutable array comprehensions*: `[: x, y for x = 1
 to 3 and y in [: "some"; "thing" :] :]`.
+
+*This extension will appear in OCaml 5.4 as the `Iarray` module. See [ocaml/ocaml#13097](https://github.com/ocaml/ocaml/pull/13097).*

jane/doc/extensions/_08-miscellaneous-extensions/labeled-tuples.md

@@ -131,3 +131,5 @@ File "foo.ml", line 3, characters 6-12:
           ^^^^^^
 Error: Could not determine the type of this partial tuple pattern.
 ```
+
+*This extension will appear in OCaml 5.4. See [ocaml/ocaml#13498](https://github.com/ocaml/ocaml/pull/13498).*