Fix TitleBlacklist support

The Commons blacklist seems to expect File: in what's checked,
presumably because that's what Special:Upload is sending it.

Change-Id: I5f502253391bbb8d255e55918bfdcfe32bd5a6cd
Bug: 65624
Mingle: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/656
Merge "Fix TitleBlacklist support"