tool: add an upper bound to avoid the breaking change in MDX

realworldocaml/mdx#446 adds an ability to run
included blocks. Our included block is not meant to be run, however,
and it appears that there's no easy way to skip the running.
So as a temporary workaround, we set the upper bound on the MDX version
until a satisfactory solution emerges.

dune-project

@@ -25,5 +25,5 @@
  (description "A pretty printer implementation of 'A Pretty Expressive Printer' (OOPSLA'23), with an emphasis on expressiveness and optimality.")
  (depends (ocaml (>= 4.05))
           dune
-          (mdx      (and (>= 2.3.0) :with-test))
+          (mdx      (and (>= 2.3.0) (<= 2.3.1) :with-test))
           (alcotest :with-test)))

pretty_expressive.opam

@@ -13,7 +13,7 @@ bug-reports: "https://github.com/sorawee/pretty-expressive-ocaml/issues"
 depends: [
   "ocaml" {>= "4.05"}
   "dune" {>= "3.10"}
-  "mdx" {>= "2.3.0" & with-test}
+  "mdx" {>= "2.3.0" & <= "2.3.1" & with-test}
   "alcotest" {with-test}
   "odoc" {with-doc}
 ]