Resolve #3512449 "Vertical tabs coming"

Closes #3512449

src/Plugin/Navigation/Extra/VersionPlugin.php

@@ -206,7 +206,7 @@ class VersionPlugin extends NavigationExtraPluginBase {
       '#open' => (bool) $triggering_element,
       '#title' => $this->t('Environments'),
       '#prefix' => '<div id="navigation-extra-version-environments-wrapper">',
-      '#postfix' => '</div>',
+      '#suffix' => '</div>',
     ];
 
     if ($triggering_element) {