The CloudBees Pipeline and CloudBees Pipeline: REST API plugins are obsolete and no longer being published.
Users who have the last releases of these, version
1.9.1, may uninstall them; new CJP Client Master releases will not include them. Similarly to the 2.x version scheme now used for the open-source Pipeline plugins, CloudBees Pipeline: Groovy Checkpoint Plugin, CloudBees Pipeline Stage View Extensions and CloudBees Pipeline: Templates Plugin will now be released with independent 2.x version numbers.
The documentation is available here.