Fix defaults for Display Title field in ManagedAdBlock.

Closes #3503691

src/Plugin/Block/ManagedAdBlock.php

@@ -65,6 +65,7 @@ class ManagedAdBlock extends BlockBase implements AdBlockInterface, ContainerFac
    */
   public function defaultConfiguration() {
     return [
+      'label_display' => FALSE,
       'ad_slot' => '',
       'ad_format' => 'responsive',
       'ad_width' => '',
@@ -118,9 +119,7 @@ class ManagedAdBlock extends BlockBase implements AdBlockInterface, ContainerFac
    * {@inheritdoc}
    */
   public function blockForm($form, FormStateInterface $form_state) {
-    // Hide block title by default.
-    $form['label_display']['#default_value'] = FALSE;
-
+    
     $link = Link::fromTextAndUrl($this->t('Google AdSense account page'), Url::fromUri('https://www.google.com/adsense/app#main/myads-springboard'))->toString();
 
     $ad_list = [];