Remove unused tasks

lib/tasks/ci/setup.rake

-namespace :ci do
-  desc "GitLab CI | Setup gitlab db"
-  task :setup do
-    Rake::Task["db:setup"].invoke
-    Rake::Task["ci:add_limits_mysql"].invoke
-  end
-end

lib/tasks/ci/sidekiq.rake

-namespace :ci do
-  namespace :sidekiq do
-    desc "GitLab CI | Stop sidekiq"
-    task :stop do
-      exec({'RAILS_ENV' => Rails.env}, 'script/background_jobs stop')
-    end
-
-    desc "GitLab CI | Start sidekiq"
-    task :start do
-      exec({'RAILS_ENV' => Rails.env}, 'script/background_jobs start')
-    end
-  end
-end