[opam] set why3 upper bound for tests

opam

@@ -136,7 +136,7 @@ depends: [
   "ocamlgraph" { with-test & >= "2.1.0" }
   "odoc" { with-doc }
   "unionFind" { >= "20220107" }
-  "why3" { >= "1.7.1" }
+  "why3" { >= "1.7.1" & (< "1.8.0" | !with-test) }
   "yaml" { >= "3.0.0" }
   "yojson" {>= "1.6.0" & (>= "2.0.1" | !with-test)}
   "zarith" { >= "1.9" }