OnyX is a multifunction utility that you can use to verify the structure of the system files, to run miscellaneous maintenance and cleaning tasks, to configure parameters in the Finder, Dock, Safari, and some Apple applications, to delete caches, to remove certain problematic folders and files, to rebuild various databases and indexes, and more.

I think it would be clearer to say 'navigate to /private/etc/cups'.

From digging around in this file, and the /var/spool/cups/ folder, I'd say this hint doesn't need to happen.
Machining cast iron tips. The CUPS system already deletes jobs once they're done - that's what the second line does. The print history doesn't take up much space at all - <1MB on my system, after a week of extensive printing. The /var/spool/cups/ files appear to be metadata on the jobs, not the jobs themselves - they're much too small.
In short, things don't seem to be broken, so I wouldn't change it unless you have a really good reason!

Interesting hint. The job history in CUPS does bother me.
Was looking at the cupsd.conf file and the default behaviour is not to keep any job files (os x 10.4.9). It does keep a list of things printed though. No need to do anything to to this line: #PreserveJobFiles No » PreserveJobFiles .
Deleting /var/spool/cups - mine is only 88K [1] So I don't feel the need to delete it - YMMV
1. sudo du -h /var/spool/cups