feat(css): Add gl-sm-pr-4 utility

mentioned in commit f725b4df

mentioned in merge request gitlab!136339 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3605 (merged)

mentioned in merge request gitlab-docs!4387 (merged)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!241 (merged)

mentioned in merge request status-page!888 (merged)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!243 (merged)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!18 (merged)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!21 (merged)