fix(GlCollapsibleListbox): fix button focus ring color in dark mode

mentioned in commit 333a4792

mentioned in merge request status-page!903

mentioned in merge request gitlab!183200 (merged)

mentioned in merge request gitlab-org/editor-extensions/gitlab-jetbrains-plugin!1551 (merged)

mentioned in merge request gitlab!183250 (closed)

mentioned in merge request gitlab!183276 (closed)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!4332 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!4333 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!4334 (closed)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!65 (merged)

mentioned in merge request gitlab-org/frontend/playground/accessibility-scanner!67 (closed)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!367 (merged)