Apply suggestions from code review

Co-authored-by: Karl Palmskog <[email protected]>

Author: gares

packages/coq-core/coq-core.8.18.0/opam

@@ -32,6 +32,9 @@ depends: [
   "zarith" {>= "1.11"}
   "ounit2" {with-test}
 ]
+conflicts: [
+  "coq"   { < "8.17" }
+]
 build: [
   # Requires dune 2.8 due to https://github.com/ocaml/dune/issues/3219
   # ["dune" "subst"] {pinned}

packages/coq/coq.8.18.0/opam

@@ -25,7 +25,7 @@ depends: [
   "coqide-server" {= version}
 ]
 build: [
-  ["dune" "subst"] {pinned}
+  ["dune" "subst"] {dev}
   [
     "dune"
     "build"