Error: Call to undefined function check_last_revised()

Problem/Motivation:

Get an error when navigating to /admin/content/needing_review

Steps to reproduce

1. Install module
2. Add field_date_last_reviewed to Article Content Type
3. Configure settings at: /admin/config/content/simple_content_notifications/settings
4. Create content and add Date Last Reviewed date and save
5. Do not see a tab for /admin/content/needing_review so entered the path in url and received the following error:

The website encountered an unexpected error. Please try again later.
Error: Call to undefined function Drupal\simple_content_notifications\Controller\check_last_revised() in Drupal\simple_content_notifications\Controller\NeedsReview->reportPage() (line 20 of modules/contrib/simple_content_notifications/src/Controller/NeedsReview.php).
Drupal\simple_content_notifications\Controller\NeedsReview->reportPage()
call_user_func_array(Array, Array) (Line: 123)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 564)
Drupal\Core\Render\Renderer->executeInRenderContext(Object, Object) (Line: 124)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->wrapControllerExecutionInRenderContext(Array, Array) (Line: 97)
Drupal\Core\EventSubscriber\EarlyRenderingControllerWrapperSubscriber->Drupal\Core\EventSubscriber\{closure}() (Line: 159)
Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object, 1) (Line: 81)
Symfony\Component\HttpKernel\HttpKernel->handle(Object, 1, 1) (Line: 58)
Drupal\Core\StackMiddleware\Session->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\KernelPreHandle->handle(Object, 1, 1) (Line: 106)
Drupal\page_cache\StackMiddleware\PageCache->pass(Object, 1, 1) (Line: 85)
Drupal\page_cache\StackMiddleware\PageCache->handle(Object, 1, 1) (Line: 48)
Drupal\Core\StackMiddleware\ReverseProxyMiddleware->handle(Object, 1, 1) (Line: 51)
Drupal\Core\StackMiddleware\NegotiationMiddleware->handle(Object, 1, 1) (Line: 23)
Stack\StackedHttpKernel->handle(Object, 1, 1) (Line: 709)
Drupal\Core\DrupalKernel->handle(Object) (Line: 19)