Duplicate values in ajaxPageState.libraries

Ensure that libraries are unique before pushing to ajax_page_state

Closes #2868737

core/modules/big_pipe/src/Render/BigPipe.php

@@ -416,7 +416,7 @@ protected function sendNoJsPlaceholders($html, $no_js_placeholders, AttachedAsse
       // - the HTML to load the CSS can be rendered.
       // - the HTML to load the JS (at the top) can be rendered.
       $fake_request = $this->requestStack->getMainRequest()->duplicate();
-      $fake_request->query->set('ajax_page_state', ['libraries' => implode(',', $cumulative_assets->getAlreadyLoadedLibraries())]);
+      $fake_request->query->set('ajax_page_state', ['libraries' => implode(',', \array_unique($cumulative_assets->getAlreadyLoadedLibraries()))]);
       try {
         $html_response = $this->filterEmbeddedResponse($fake_request, $html_response);
       }