Fix accessibility on tabbed partial

[Stef-Rousset]

🎩 What? Why?

This PR improves accessibility on tabbed partial :

• it removes the role="menu" on ul id="dropdown-menu-pages" and role="menuitem" on li
• it prevents the changing of aria-hidden value on ul id="dropdown-menu-pages" when clicking on window
• it changes the value of aria-current on active a by for "page"

Those issues come from the audit of Angers city (page 56), and they refer to criterias 2.5.3, 4.1.2, 1.3.2, 4.1.2, 1.3.3 and 4.1.1 from WCAG

📌 Related Issues

• Related to https://github.com/orgs/OpenSourcePolitics/projects/26/views/1?pane=issue&itemId=112723283&issue=OpenSourcePolitics%7Cintern-tasks%7C48

Testing

1. As a user, go to the footer of decidim page and in "Help" column, click on "General"
2. Open you devTools, check that the ul id="dropdown-menu-pages" and its li children have no attribute role
3. Check inside active li that the a link has a aria-current="page", and check that inside non active li the aria-current on a has a false value
4. Click anywhere on window and check that ul aria-hidden attribute value is still false

📷 Screenshots (optional)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions. @carolromero & @xabier feel free to chime in.