Follow-up from "Keep visual edge with icons and chevron"

The following discussion from !116963 (merged) should be addressed:

• @sdejonge started a discussion:

  suggestion (non-blocking): the <hr> element is read by screen-readers it would be good to use aria-hidden="true" to reduce noise as it's decorative in the sidebar.

      <hr aria-hidden="true" class="gl-my-2 gl-mx-4" />

  In the HTML spec for <hr>:

  The hr element represents a paragraph-level thematic break, e.g. a scene change in a story, or a transition to another topic within a section of a reference book.