Random failing test

Describe your bug or feature request.

We have ProductLayoutBuilderIntegrationTest that fails randomly when checking whether the element doesn't exist after the AJAX submission.

I guess what is happening here is that the AJAX commands returned by the request don't have time to be executed before $assert_session->assertNoElementAfterWait('css', '#drupal-off-canvas');.

What I recommend is replacing

    $assert_session->assertWaitOnAjaxRequest();
    $assert_session->assertNoElementAfterWait('css', '#drupal-off-canvas');

with

    $assert_session->waitForElementRemoved('css', '#drupal-off-canvas');