[Redesign] Thinner PHUIPinboardItemView

Summary: Ref T8099, Cleaner, thinner layout for PHUIPinboardItemView. Removes inner padding, cleans UI by putting title underneath image.

Test Plan:
Review Macro, Pholio, Dashboards with Pholio

{F422185}

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T8099

Differential Revision: https://secure.phabricator.com/D12987