Upgrade to Ruby 2.6.5
This brings the code base in line with the same Ruby version used by GitLab CE/EE.
Fix new Rubocop errors
Edited by George Koltsov
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
This brings the code base in line with the same Ruby version used by GitLab CE/EE.
Fix new Rubocop errors