mirage 4.10: restrict to ocaml < 5 for tests

-  Error: Unbound value Unikernel_make__4.start'
-  Hint: Did you mean start?
+  Error: Unbound value "Unikernel_make__4.start'"
+  Hint: Did you mean "start"?

as we do for earlier mirage releases

Author: hannesm

packages/mirage/mirage.4.10.0/opam

@@ -19,6 +19,7 @@ build: [
 
 depends: [
   "ocaml" {>= "4.13.0"}
+  "ocaml" {with-test & < "5"}
   "dune" {>= "2.9.0"}
   "astring"
   "cmdliner" {>= "1.2.0"}