Revert GraphQL API reference

.gitlab/issue_templates/Security developer workflow.md

doc/README.md

doc/api/api_resources.md

doc/api/epics.md

doc/api/issues.md

doc/api/merge_requests.md

doc/api/todos.md

doc/api/v3_to_v4.md

doc/development/api_styleguide.md

doc/development/documentation/styleguide.md

doc/operations/incident_management/alert_details.md

doc/university/README.md

doc/user/admin_area/settings/external_authorization.md

doc/user/group/saml_sso/index.md

doc/user/index.md

doc/user/profile/preferences.md

doc/user/project/issues/due_dates.md

doc/user/project/issues/issue_data_and_actions.md

doc/user/todos.md