Fix nested <ul>markup in non-static menu sections

What does this MR do and why?

Fix invalid HTML markup in super sidebar

• Ensure <li> elements are children of <ul>
• Update aria-hidden to aria-hidden="true"
• Add aria-labelledby heading for <nav>
• Update menu heading for <ul> to <h3> add aria-labelledby

Changelog: fixed

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Review super sidebar contents in accessibility tree (Chrome | Firefox)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #425396 (closed)