feat(GlInputGroupText): add default styling for GlInputGroupText

mentioned in commit 8ae1e1f0

mentioned in merge request status-page!838 (merged)

mentioned in merge request gitlab-org/frontend/pajamas-adoption-scanner!168 (merged)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3432 (merged)

mentioned in merge request gitlab-docs!4099 (merged)

mentioned in merge request gitlab!126562 (merged)

mentioned in merge request gitlab!128113 (closed)

mentioned in merge request gitlab-org/gitlab-services/design.gitlab.com!3479 (merged)