instance

If you want to remove a custom update center as an updates source, simply uninstall or disable the custom update center installer plugin and restart your Jenkins instance. The list of update centers will not be modified on disk as a result of the change, but the custom update center will not be loaded into the list of update centers and you will see the following

WARNING: Failed to resolve class com.thoughtworks.xstream.mapper.CannotResolveClassException: custom

in your logs until the list of update centers is re-saved to disk.