HG-228: Removed unused import

This logic (which was taking care of the ads on the first load page) is moved to the Mercury client code now. The reason This gives us to get rid of the global objects `Wikia.article.adsContext` and `Wikia.ads.slots` and gives us better control over the ads.

Relevant PR from the Mercury repo https://github.com/Wikia/mercury/pull/274

/cc @gabrys can you take a look please
Trailing comma is generally good in PHP IMO. Doesn't diff as two lines when you add new item.