fix(UIShell): use hr instead of li with role

[tw15egan]

Closes #14479

Refactors UI Shell Side Nav Separator to use an hr instead of a li with `role="separator" to fix an a11y issue

Changelog

Changed

• changed li to hr, added styles to match current

Removed

• unnecessary role

Testing / Reviewing

Run a11y checker on a UI Shell story with a side nav separator and ensure there are no violations

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[alisonjoseph]

I don't believe it's valid html to have a hr as a child of ul
https://html.spec.whatwg.org/multipage/grouping-content.html#the-hr-element

other than that it looks fine and doesn't have any a11y checker errors 🤔

Likely the correct html for this would require two separate lists with a hr in between (likely not a simple update)

[alisonjoseph]

https://deploy-preview-14723--v11-carbon-react.netlify.app/iframe.html?args=&id=components-ui-shell-sidenav--fixed-side-nav-w-divider&viewMode=story

I think it depends on where it's being used.

[tw15egan]

@alisonjoseph can we just wrap it in anli? We have buttons as nested elements in li for the nested menus, so I would imagine that's fine then?

[alisonjoseph]

@tw15egan oh yea, good idea. I don't see why not 👍

[tw15egan]

@alisonjoseph updated 👍

[alisonjoseph]

LGTM, no a11y errors

[carbon-automation]

Hey there! v11.39.0 was just released that references this issue/PR.