Updated Phrequent "Time Tracked" page to show time in Started / Ended columns.

Summary:
Small update that shows time as well as date on the Time Tracked page, which
is important given that durations are likely to be less than a day.

Test Plan: Apply the patch and view the "Time Tracked" page under Phrequent.

Reviewers: epriestley

CC: aran, Korvin

Maniphest Tasks: T2857

Differential Revision: https://secure.phabricator.com/D5482