Returns HTML for the first page in the process of updating projects.
$variables: An associative array containing:
function theme_update_manager_update_form($variables) {
$form = $variables['form'];
$last = state()
->get('update.last_check') ?: 0;
$output = theme('update_last_check', array(
'last' => $last,
));
$output .= drupal_render_children($form);
return $output;
}