Issue #3413647: Fix HTML tags getting double-encoded in data-caption

Closes #3413647

src/Form/EntityEmbedDialog.php

@@ -537,7 +537,6 @@ class EntityEmbedDialog extends FormBase {
         '#type' => 'textarea',
         '#rows' => 3,
         '#default_value' => isset($entity_element['data-caption']) ? Html::decodeEntities($entity_element['data-caption']) : '',
-        '#element_validate' => ['::escapeValue'],
       ];
     }
 
@@ -850,18 +849,6 @@ class EntityEmbedDialog extends FormBase {
     return $response;
   }
 
-  /**
-   * Form element validation handler; Escapes the value an element.
-   *
-   * This should be used for any element in the embed form which may contain
-   * HTML that should be serialized as an attribute element on the embed.
-   */
-  public static function escapeValue($element, FormStateInterface $form_state) {
-    if ($value = trim($element['#value'])) {
-      $form_state->setValueForElement($element, Html::escape($value));
-    }
-  }
-
   /**
    * Returns the allowed display plugins given an embed button and an entity.
    *