Swift: remove wikimania2006 exception

It seems that wikimania2006 isn't actually different from any other
wikimania years. And while wikimania$YEAR.wikipedia.org doesn't exist in
DNS, MediaWiki happily accepts it and serves thumbnails, so one
exception less.

Change-Id: Ief61ad9df880cc0d6c43ce6992795e4ec6f7e0f5