Show only recent open revisions affecting the same files

Summary: Fixes T5658. Over a long period of time, some cruft can build up here. Only show revisions which have been updated in the last 30 days.

Test Plan:

• Viewed panel in Differential and Diffusion.
• Changed limit from 30 days to 30 seconds and saw no revisions.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T5658

Differential Revision: https://secure.phabricator.com/D12158