Correct language code: Wikimedia's roa-rup is MediaWiki's rup

https://meta.wikimedia.org/wiki/Special_language_codes
https://roa-rup.wikipedia.org/w/api.php?action=query&meta=siteinfo

Spotted by the roa-rup editor with countless pen names, who's
making a lot of translations lately.

Change-Id: If46d92f9849f87c6b781e6327caf17a95b669c7c
Merge "Correct language code: Wikimedia's roa-rup is MediaWiki's rup"