Resolve #3486079 "Pasting update clipboard"

Closes #3486079

tests/src/FunctionalJavascript/FootnotesCkeditorPluginTest.php

@@ -157,6 +157,7 @@ class FootnotesCkeditorPluginTest extends WebDriverTestBase {
 
       // Verify the content is correctly pasted.
       $this->assertSession()->waitForField('body[0][value]', 1000);
+      $this->assertSession()->waitForElement('css', 'span.footnotes-preview[data-footnotes-preview="ready"]', 1000);
       $page = $this->getSession()->getPage();
 
       $ckeditorContent = $page->find('css', '.ck-editor__editable')->getHtml();