Currently, the way to disable external links from showing in the printable version of a page is to modify skins/common/commonPrint.css. [[mw:Manual:FAQ#How_do_I_disable_external_links_from_showing_in_the_printable_version_of_a_page.3F]].
There should be a config setting for this to reduce the number of files that have to be edited to configure one's wiki. Also, this will prevent the modification from being overwritten when one upgrades MediaWiki.
Version: 1.23.0
Severity: enhancement