Note language links need to be edited on Wikidata

It wasn't true when we wrote this message, but now most of the language
links on most of the wikis are edited via Wikidata, rather than source
editing mode, so tweak the message accordingly.

Bug: 51816
Change-Id: Id11d1af397314030c3c74aa029974fcdfd9e10df
Merge "Note language links need to be edited on Wikidata"