Fix cursor on mock card hover in pholio

Summary: Fixes T4888, make seemingly actionable area in Pholio "Mocks List" actually actionable

Test Plan: Open pholio, create a mock, return to list of all mocks, hover over mock, only image in mock should switch to pointer on hover.

Reviewers: chad, #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T4888

Differential Revision: https://secure.phabricator.com/D8986