Replace GITLAB with GitLab in rake task descriptions

lib/tasks/cache.rake

lib/tasks/dev.rake

lib/tasks/gitlab/backup.rake

lib/tasks/gitlab/bulk_add_permission.rake

lib/tasks/gitlab/check.rake

lib/tasks/gitlab/cleanup.rake

lib/tasks/gitlab/enable_automerge.rake

lib/tasks/gitlab/generate_docs.rake

lib/tasks/gitlab/import.rake

lib/tasks/gitlab/info.rake

lib/tasks/gitlab/setup.rake

lib/tasks/gitlab/shell.rake

lib/tasks/gitlab/test.rake

lib/tasks/gitlab/web_hook.rake

lib/tasks/migrate/add_limits_mysql.rake

lib/tasks/migrate/migrate_iids.rake

lib/tasks/setup.rake

lib/tasks/sidekiq.rake

lib/tasks/test.rake