Merge branch '474513-broadcast-notifications-affects-the-broadcast-message-height-style-property' into 'master' 

Make sure broadcast notifications do not affect broadcast message height

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/160787



Merged-by: Eduardo Sanz García <esanz-garcia@gitlab.com>
Approved-by: Eduardo Sanz García <esanz-garcia@gitlab.com>
Reviewed-by: Eduardo Sanz García <esanz-garcia@gitlab.com>
Co-authored-by: Chad Lavimoniere <clavimoniere@gitlab.com>