Refresh: Update Tooltip designs

Created by: umpox

Issue: https://github.com/sourcegraph/sourcegraph/issues/21188

Designs: https://www.figma.com/file/NIsN34NH7lPu04olBzddTw/Design-Refresh-Systemization-source-of-truth?node-id=3131%3A38534

Minor updates as the color change was updated as part of the global colors PR.

Changed the file structure to move Tooltip.scss to the rest of our 'global' stylesheets as it directly modifies a Bootstrap class