Remove temporary border override to remove halo effect
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Let's remove this temporary `gl-border-0` that was added to fix the halo effect once there is a fix in gitlab-ui

The following discussion from !32821 should be addressed:
- [ ] @sming-gitlab started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/32821#note_348594114): (+1 comment)
> @mrincon tagging you to review since we both had a similar issue with this. I decided not to opt for your override path. Since this issue has a weight of `1`, I thought it's best to keep the changes to a minimum. (I think I'll also create a separate issue to clean up this override once there's a solution on gitlab-ui). Anyways, do you mind reviewing this and see if my solution is okay :grinning:
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