workflow_list_title on history overview is unneeded

Drupal core might've fixed this at some point, but the title inserted in the transition list builder isn't needed any longer, at least from what I can tell.

Inside Drupal\workflow\Controller\WorkflowTransitionListController (~line 129)

Remove:

    $form['workflow_list_title']['#weight'] = 200;

Inside Drupal\workflow\WorkflowTransitionListBuilder (~line 227)

Remove:

    // @todo d8-port: get core title working: $build['table']['#title'] by getTitle() is not working.
    $build['workflow_list_title'] = array(
      '#markup' => $this->getTitle(),
    );