nixos/quassel: replace deprecated usage of PermissionsStartOnly

see https://github.com/NixOS/nixpkgs/issues/53852

nixos/modules/services/networking/quassel.nix

@@ -104,6 +104,10 @@ in
         gid = config.ids.gids.quassel;
       }];
 
+    systemd.tmpfiles.rules = [
+      "d '${cfg.dataDir}' - ${user} - - -"
+    ];
+
     systemd.services.quassel =
       { description = "Quassel IRC client daemon";
 
@@ -111,11 +115,6 @@ in
         after = [ "network.target" ] ++ optional config.services.postgresql.enable "postgresql.service"
                                      ++ optional config.services.mysql.enable "mysql.service";
 
-        preStart = ''
-          mkdir -p ${cfg.dataDir}
-          chown ${user} ${cfg.dataDir}
-        '';
-
         serviceConfig =
         {
           ExecStart = concatStringsSep " " ([
@@ -126,7 +125,6 @@ in
           ] ++ optional cfg.requireSSL "--require-ssl"
             ++ optional (cfg.certificateFile != null) "--ssl-cert=${cfg.certificateFile}");
           User = user;
-          PermissionsStartOnly = true;
         };
       };