Untitled

/**
 * Implements template_preprocess_HOOK() for form templates.
 */
function YOUR_THEME_preprocess_form_element(&$variables) {
  // Check if the form element is of type 'text_format' and has the attribute to disable CKEditor shim.
  if ($variables['element']['#type'] === 'text_format' && isset($variables['element']['#attributes']['data-ckeditor-shim-disabled'])) {
    // Get the CSS array and remove the CKEditor v4-shims.css file.
    $css = &$variables['element']['#attached']['library'];
    $css = array_diff($css, ['ckeditor/drupal.ckeditor.v4-shims']);
  }
}