[random test failure] CKEditor5MarkupTest

Problem/Motivation

See https://git.drupalcode.org/project/drupal/-/jobs/5012708

  CKEditor5Markup (Drupal\Tests\ckeditor5\FunctionalJavascript\CKEditor5Markup)
     ✔ Attribute encoding
     ✔ Filter html allowed global attributes
     ✘ Comments
       ┐
       ├ Behat\Mink\Exception\ExpectationException: The string "This is a test!" was not found anywhere in the HTML response of the current page.
       │
       │ /builds/project/drupal/vendor/behat/mink/src/WebAssert.php:888
       │ /builds/project/drupal/vendor/behat/mink/src/WebAssert.php:363
       │ /builds/project/drupal/core/tests/Drupal/Tests/WebAssert.php:559
       │ /builds/project/drupal/core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5MarkupTest.php:194
       ┴
     ✔ Styles and scripts
    

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

Introduced terminology

API changes

Data model changes

Release notes snippet