feat(Toggle): Change icon size to xs

mentioned in merge request !4512 (merged)

mentioned in commit 7710a142

mentioned in merge request status-page!903

mentioned in merge request gitlab!163043 (closed)

mentioned in merge request gitlab!163047 (closed)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!4003 (merged)

mentioned in merge request gitlab!163601 (merged)

mentioned in merge request gitlab!163882 (closed)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!342 (merged)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!49 (merged)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!343 (merged)