fix: GlTokenSelector: make it possible to focus input field with Tab button

mentioned in commit b6c5d7d4

mentioned in merge request gitlab!90318 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2906 (merged)

mentioned in merge request status-page!546 (merged)

mentioned in merge request gitlab-docs!2841 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!2914 (closed)