Improve the `spec/frontend/super_sidebar/components/sidebar_menu_spec.js`

The following discussions from !120522 (merged) should be addressed:

• @f_caplette started a discussion:

  Suggestion - non-blocking This is a little bit hard to reason with since we have twice the same generic word, item.items. It's hard to know what is the item and what are items 😅

  Perhaps just:

      isSection(navEntity) {
        return navEntity.items?.length;

  It's not a huge improvement but it helps understand a bit more that the navEntity here might be a section if it has items. WDYT?

• @f_caplette started a discussion:

  Suggestion - non-blocking Perhaps the sidebarData could be the default value in the factory function to avoid passing it in every factory call, WDYT?

• @f_caplette started a discussion:

  Issue I know this is outside of this MR and I am fine for this being addressed in a follow up. However, with the Vue3 migration, we simply cannot have assertions on the vm anymore. Do we have an existing follow up already for these to be replaced with Vue3 compliant tests or should we create one now? 🤔