Issue #3182458: search results "empty" message: fix skipped heading level

Closes #3182458

core/modules/search/src/Controller/SearchController.php

@@ -118,7 +118,7 @@ public function view(Request $request, SearchPageInterface $entity) {
       '#theme' => ['item_list__search_results__' . $plugin->getPluginId(), 'item_list__search_results'],
       '#items' => $results,
       '#empty' => [
-        '#markup' => '<h3>' . $this->t('Your search yielded no results.') . '</h3>',
+        '#markup' => '<p>' . $this->t('Your search yielded no results.') . '</p>',
       ],
       '#list_type' => 'ol',
       '#context' => [