fix(css): Fix @error call by adding expression

mentioned in commit f8636b5b

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2607 (merged)

mentioned in merge request status-page!399 (merged)

mentioned in merge request gitlab-docs!2230 (merged)

mentioned in merge request gitlab-docs!2232 (closed)

mentioned in merge request gitlab!73463 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2611 (merged)

mentioned in merge request gitlab-docs!2242 (merged)

mentioned in merge request gitlab-docs!2245 (closed)