Don't use an undefined index if not needed

It is not set. And not used. Just some copy paste leftover.

Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

core/templates/loginflowv2/done.php

@@ -25,8 +25,6 @@ declare(strict_types=1);
 style('core', 'login/authpicker');
 
 /** @var array $_ */
-/** @var \OCP\IURLGenerator $urlGenerator */
-$urlGenerator = $_['urlGenerator'];
 ?>
 
 <div class="picker-window">