improvedDef/sshAuth: workaround issue with conflicting settings

- until https://github.com/NixOS/nixpkgs/pull/339786 gets merged
- testdriver sets PermitRootLogin = "yes" (priority 100)
- PR will change that to a mkDefault, as it is not required for a
  functional installer

nix/nixos-modules/improvedDefaults/sshAuthorize.nix

@@ -56,8 +56,9 @@ in
         in
         {
 
+          # TODO mkOverride until https://github.com/NixOS/nixpkgs/pull/339786
           services.openssh.settings.PermitRootLogin =
-            if isRootAuthed then "prohibit-password" else lib.mkDefault "no";
+            if isRootAuthed then lib.mkOverride 99 "prohibit-password" else lib.mkDefault "no";
 
           users.users.root.openssh.authorizedKeys.keys = lib.mkIf doRootAuth (
             lib.mkDefault myOpts.sshPublicKeys