fix(modal): Remove depreacted button variants from modals

mentioned in commit bd592c70

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2263 (merged)

mentioned in merge request status-page!239 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2266 (merged)

mentioned in merge request status-page!240 (merged)

mentioned in merge request gitlab!55107 (merged)

mentioned in merge request gitlab-docs!1564 (merged)

mentioned in commit f4d59483