Reorganize escaping in DifferentialRevisionUpdateHistoryView

Summary:
Escaped $id is compared with non-escaped $max_id.
Escaped $id is escaped again in phutil_render_tag().

Note: $id is numeric :-).

Test Plan: Display diff.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1580