R1:92c4dfdfb19c

Fix an extra %s in BlogFeedController

Summary: Fished this out of the secure.phabricator.com error log. Introduced in D4869.

Test Plan: Eyeballed it.

Reviewers: chad, vrana

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D5199