Update Grape from 0.13.0 to 0.15.0
Changelog: https://github.com/ruby-grape/grape/blob/v0.15.0/CHANGELOG.md
Working on #18226 (closed).
cc: @DouweM
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Changelog: https://github.com/ruby-grape/grape/blob/v0.15.0/CHANGELOG.md
Working on #18226 (closed).
cc: @DouweM