Issue #3306720 by Spokje: Replace ckeditor with ckeditor5 in...

Issue #3306720 by Spokje: Replace ckeditor with ckeditor5 in twig_theme_test.attach_library.html.twig

(cherry picked from commit e09d527a)

core/modules/system/tests/modules/twig_theme_test/templates/twig_theme_test.attach_library.html.twig

-{{ attach_library('core/ckeditor') }}
+{{ attach_library('core/ckeditor5') }}

core/modules/system/tests/src/Functional/Theme/EngineTwigTest.php

@@ -144,7 +144,7 @@ public function testTwigFileUrls() {
    */
   public function testTwigAttachLibrary() {
     $this->drupalGet('/twig-theme-test/attach-library');
-    $this->assertSession()->responseContains('ckeditor.js');
+    $this->assertSession()->responseContains('ckeditor5-dll.js');
   }
 
   /**