Update packages/letters/letters.0.4.0/opam

Author: mseri

packages/letters/letters.0.4.0/opam

@@ -29,7 +29,7 @@ depends: [
   "odoc" {with-doc}
   "ocamlformat" {dev}
 ]
-conflicts: ["rresult"] {< "0.7.0"}
+conflicts: ["rresult" {< "0.7.0"}]
 build: [
   ["dune" "subst"] {dev}
   [