feat(DuoChat): Make DuoChat fullWidth by default

mentioned in commit b1d34939

mentioned in merge request status-page!903

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!26 (closed)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!300 (merged)

mentioned in merge request gitlab!146367 (merged)

mentioned in merge request gitlab!146672 (merged)

mentioned in merge request gitlab!146682 (closed)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3770 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3771 (merged)