(bug 45696) Add a msg to $wgForceUIMsgAsContentMsg for Wikidata

Adding 'sitesupport-url' to $wgForceUIMsgAsContentMsg for Wikidata
so that the message can be translated into user's interface lang.

Bug: 45696
Change-Id: I11118b4b81f5c0a47872b4ecf81c916ed20c8922