Update tooltip values to meet design specs
What does this MR do?
As part of the design system clean-up, this merge request updates the tooltip component CSS to meet design specs.
New merge request in favor of https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/28486
Closes gitlab-ui#264 (closed) and https://gitlab.com/gitlab-org/design.gitlab.com/issues/285
Edited by Rayana Verissimo