meld.updateScript: remove version policy

Stable version was buggy so we are tracking unstable ones.

pkgs/applications/version-management/meld/default.nix

···
   passthru = {
     updateScript = gnome.updateScript {
       packageName = pname;
-      versionPolicy = "odd-unstable";
+      versionPolicy = "none"; # should be odd-unstable but we are tracking unstable versions for now
     };
   };