Filter news from the sub-topic 'A-Z' list

Story: https://www.pivotaltracker.com/story/show/82281582

Exclude news articles from the 'A-Z' list, mitigating the user
impact of a department tagging loosely related news content to a
sub-topic when there is no curated list.
After speaking with Content, we need to add `world_location_news_article` to this list.