chore: Use native ul/li elements for slider labels

[avinashbot]

Description

See #3359 for context — touching that file revealed a broken a11y test; which this PR hopefully addresses.

Related links, issue #, if available: n/a

How has this been tested?

The added test was failing because it preferred using native elements; I wasn't sure why they couldn't be used either, so I'm testing that out in this PR.

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.45%. Comparing base (720d3e0) to head (c429c62).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3376   +/-   ##
=======================================
  Coverage   96.45%   96.45%           
=======================================
  Files         802      802           
  Lines       22889    22889           
  Branches     7848     7909   +61     
=======================================
  Hits        22078    22078           
  Misses        757      757           
  Partials       54       54           

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