R1:a7a3c90f145b

Fix a file name to match the PHP class name

Summary: This was misnamed in D11177.

Test Plan: `arc lint`

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D11193