Warn users of pre-release versions of opam 2.4 to update

Author: kit-ty-kate

repo

@@ -7,7 +7,8 @@ announce: [
 """ { opam-version < "2.0.10" |
       (opam-version >= "2.1.0~~" & opam-version < "2.1.6") |
       (opam-version >= "2.2.0~~" & opam-version < "2.2.1") |
-      (opam-version >= "2.3.0~~" & opam-version < "2.3.0") }
+      (opam-version >= "2.3.0~~" & opam-version < "2.3.0") |
+      (opam-version >= "2.4.0~~" & opam-version < "2.4.0") }
 """
 [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~~"}