Prefer U2F as 2FA method if it is available.

src/Controller/UserController.php

@@ -82,7 +82,7 @@ class UserController extends AdminPages\BaseAdminController
     }
 
     /**
-     * @Route("/{id}", name="user_delete", methods={"DELETE"})
+     * @Route("/{id}", name="user_delete", methods={"DELETE"}, requirements={"id"="\d+"})
      */
     public function delete(Request $request, User $entity, StructuralElementRecursionHelper $recursionHelper)
     {
@@ -153,7 +153,6 @@ class UserController extends AdminPages\BaseAdminController
         ]);
     }
 
-
     /**
      * Get either a Gravatar URL or complete image tag for a specified email address.
      *