Fixed Rubocop offenses

lib/gitlab/markdown/filter/table_of_contents_filter.rb

lib/rouge/formatters/html_gitlab.rb

spec/factories.rb

spec/features/security/group_access_spec.rb

spec/helpers/groups_helper.rb

spec/models/ci/commit_spec.rb

spec/models/key_spec.rb

spec/models/project_services/hipchat_service_spec.rb

...odels/project_services/slack_service/note_message_spec.rb

spec/models/user_spec.rb

spec/requests/api/merge_requests_spec.rb

spec/requests/api/services_spec.rb

spec/services/create_commit_builds_service_spec.rb

spec/services/git_tag_push_service_spec.rb

spec/services/update_snippet_service_spec.rb

spec/support/repo_helpers.rb

spec/workers/repository_fork_worker_spec.rb

spec/workers/stuck_ci_builds_worker_spec.rb