filter_phids => filterPHIDs

Summary: typo of sorts. should probably be philterPHIDs. :P

Test Plan: verified i spelled "filterPHIDs" correctly.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1993

Differential Revision: https://secure.phabricator.com/D3846