nixos/qbittorrent: add maintainer undefined-landmark

As discussed in PR #287923. The author agreed to add me as a maintainer
to the module after merging.

nixos/modules/services/torrent/qbittorrent.nix

···
       ++ optionals (cfg.torrentingPort != null) [ cfg.torrentingPort ]
     );
   };
-  meta.maintainers = with maintainers; [ fsnkty ];
+  meta.maintainers = with maintainers; [
+    fsnkty
+    undefined-landmark
+  ];
 }

nixos/tests/qbittorrent.nix

···
   name = "qbittorrent";
 
   meta = with pkgs.lib.maintainers; {
-    maintainers = [ fsnkty ];
+    maintainers = [
+      fsnkty
+      undefined-landmark
+    ];
   };
 
   nodes = {