reverted:
--- b/core/modules/outside_in/outside_in.module
+++ a/core/modules/outside_in/outside_in.module
@@ -10,8 +10,6 @@
 use Drupal\outside_in\Block\BlockEntityOffCanvasForm;
 use Drupal\outside_in\Form\SystemBrandingOffCanvasForm;
 use Drupal\outside_in\Form\SystemMenuOffCanvasForm;
-use Drupal\Core\StringTranslation\StringTranslationTrait;
-use Drupal\Core\StringTranslation\TranslationInterface;
 
 /**
  * Implements hook_help().
@@ -19,11 +17,11 @@
 function outside_in_help($route_name, RouteMatchInterface $route_match) {
   switch ($route_name) {
     case 'help.page.outside_in':
+      $output = '<h3>' . t('About') . '</h3>';
+      $output .= '<p>' . t('The Settings Tray module provides an \'edit mode\' in which clicking on a block opens a slide-out tray which allows configuration to be altered without leaving the page.For more information, see the <a href=":outside-in-documentation">online documentation for the Settings Tray module</a>.', [':outside-in-documentation' => 'https://www.drupal.org/documentation/modules/outside_in']) . '</p>';
+      $output .= '<h3>' . t('Uses') . '</h3>';
-      $output = '<h3>' . $this->t('About') . '</h3>';
-      $output .= '<p>' . $this->t('The Settings Tray module provides an \'edit mode\' in which clicking on a block opens a slide-out tray which allows configuration to be altered without leaving the page.For more information, see the <a href=":outside-in-documentation">online documentation for the Settings Tray module</a>.', [':outside-in-documentation' => 'https://www.drupal.org/documentation/modules/outside_in']) . '</p>';
-      $output .= '<h3>' . $this->t('Uses') . '</h3>';
       $output .= '<dl>';
+      $output .= '<dt>' . t('Editing blocks on the same page in the slide-out tray') . '</dt>';
-      $output .= '<dt>' . $this->t('Editing blocks on the same page in the slide-out tray') . '</dt>';
       $output .= '</dl>';
       return ['#markup' => $output];
   }
diff -u b/core/modules/outside_in/src/Cache/Context/OutsideInCacheContext.php b/core/modules/outside_in/src/Cache/Context/OutsideInCacheContext.php
--- b/core/modules/outside_in/src/Cache/Context/OutsideInCacheContext.php
+++ b/core/modules/outside_in/src/Cache/Context/OutsideInCacheContext.php
@@ -5,8 +5,6 @@
 use Drupal\Core\Cache\CacheableMetadata;
 use Drupal\Core\Cache\Context\CacheContextInterface;
 use Drupal\outside_in\OutsideInManagerInterface;
-use Drupal\Core\StringTranslation\StringTranslationTrait;
-use Drupal\Core\StringTranslation\TranslationInterface;
 
 /**
  * Defines the OutsideInCacheContext service, for "Outside-In or not" caching.
diff -u b/core/modules/outside_in/src/Form/SystemBrandingOffCanvasForm.php b/core/modules/outside_in/src/Form/SystemBrandingOffCanvasForm.php
--- b/core/modules/outside_in/src/Form/SystemBrandingOffCanvasForm.php
+++ b/core/modules/outside_in/src/Form/SystemBrandingOffCanvasForm.php
@@ -43,7 +43,7 @@
    */
   public function __construct(ConfigFactoryInterface $config_factory, TranslationInterface $string_translation) {
     $this->configFactory = $config_factory;
-    $this->stringTranslation = $string_translation;
+    setStringTranslation($string_translation);
   }
 
   /**