MR discussion bottom rounded border is not connected nicely

The following discussion from gitlab-ce!28185 should be addressed:

• @pslaughter started a discussion: (+1 comment)

  note: Unfortunately this introduces a small visual regression. The bottom rounded border is not connected nicely. This is probably because the surrounding border is not handled by a single element (instead some elements add the side border and others the top and bottom one).

  

  We should probably create a follow up issue for this...

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