feat(css): Add a 600 red left inset border of size 3

mentioned in commit 4b83043b

mentioned in merge request status-page!473 (merged)

mentioned in merge request gitlab!82590 (closed)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2746 (closed)

mentioned in merge request gitlab-docs!2490 (merged)

mentioned in merge request gitlab!83216 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2755 (merged)