Improve the announcement message inviting to upgrade opam when using …

…opam 2.0

Co-authored-by: Anil Madhavapeddy <anil@recoil.org>

repo

@@ -6,7 +6,7 @@ announce: [
 [WARNING] opam is out-of-date. Please consider updating it (https://opam.ocaml.org/doc/Install.html)
 """ {(opam-version >= "2.1.0~~" & opam-version < "2.1.6") | opam-version < "2.0.10" | (opam-version >= "2.2.0~~" & opam-version < "2.2.1")}
 """
-[INFO] opam 2.1 and 2.2 include many performance improvements over 2.0; please consider upgrading (https://opam.ocaml.org/doc/Install.html)
+[INFO] opam 2.1 and 2.2 include many performance and security improvements over 2.0; please consider upgrading (https://opam.ocaml.org/doc/Install.html)
 """ {opam-version >= "2.0.10" & opam-version < "2.1.0~~"}
 """
 [WARNING] please ensure to have GNU patch installed as `patch`. Otherwise update may fail silently (since it can't remove files).