CSS classes are not generated for container

Problem/Motivation

After upgrade from D9 to Drupal 10.2.6 some of the CSS classes got missing from container template (_containers.twig).

Proposed resolution

Problem is, that attributes.class|keys return integer keys and not the class names. So this expression 'form-actions' in attributes.class|keys is always false.

To fix the problem, keys filter should be removed.