Changed tooltip and pop-over documentation to let those elements spawn above the…

What does this MR do?

Changed tooltip and pop-over documentation to let those elements spawn above the target element by default

What are the relevant issue numbers?

• https://gitlab.com/gitlab-org/gitlab-ce/issues/48581
• https://gitlab.com/gitlab-org/gitlab-ce/issues/39044#note_43245858

closes gitlab-org/gitlab-design#190 (closed)