feat(GlDuoChat): switched /test to /tests command

mentioned in commit 753db023

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

mentioned in merge request gitlab!138915 (merged)

mentioned in merge request !3839 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3654 (merged)

mentioned in merge request gitlab-docs!4463 (merged)

mentioned in merge request status-page!891 (merged)

mentioned in merge request status-page!893 (merged)

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