fix(GlBroadcastMessage): use ds shadow and overlap background

See merge request gitlab-org/gitlab-ui!4815



Merged-by: Olena Horal-Koretska <ohoralkoretska@gitlab.com>
Approved-by: Jeremy Elder <jelder@gitlab.com>
Approved-by: Olena Horal-Koretska <ohoralkoretska@gitlab.com>
Co-authored-by: GitLab Bot <gitlab-bot@gitlab.com>
Co-authored-by: danmh <dmizzi-harris@gitlab.com>

## [102.1.5](gitlab-org/gitlab-ui@v102.1.4...v102.1.5) (2024-11-14)

### Bug Fixes

* **GlBroadcastMessage:** use ds shadow and overlap background ([0ffc7c9e](gitlab-org/gitlab-ui@0ffc7c9e))