#3423414: Remove deprecated code and updated drupal root path retrieval

src/Form/LoggerFileForm.php

@@ -32,6 +32,13 @@ class LoggerFileForm extends PluginFormBase implements ContainerInjectionInterfa
    * @var \Drupal\Core\File\FileSystemInterface
    */
   protected $fileSystem;
+  
+  /**
+   * The Drupal root directory.
+   *
+   * @var string
+   */
+  protected $drupalRoot;
 
   /**
    * Creates a config form for a file logger.
@@ -60,7 +67,7 @@ class LoggerFileForm extends PluginFormBase implements ContainerInjectionInterfa
       $container->get('plugin.manager.monitoring_file_log_formatter'),
       $container->get('string_translation'),
       $container->get('file_system'),
-      $container->get('app.root')
+      $container->getParameter('app.root')
     );
   }