fix: #3520036 [random test failure] CKEditor5MarkupTest

Derek Wrightrequested to merge
issue/drupal-3520036:3520036-random-test-fail-CKEditor5MarkupTest into 11.x

Closes #3520036

REPEAT_TEST_CLASS : Drupal\Tests\ckeditor5\FunctionalJavascript\CKEditor5MarkupTest
REPEAT_COUNT : 250

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