memento_updater: Remove deprecated files.

The review settings files were for old Rietveld code review system.
It's no longer required for current Gerrit system.

BUG=none
TEST=emerge-link memento_softwareupdate # success

Change-Id: Ie4de055652e5ed80a493422d95ce7903c652adf6
Reviewed-on: https://chromium-review.googlesource.com/178381
Tested-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Rong Chang <rongchang@chromium.org>
Commit-Queue: Hung-Te Lin <hungte@chromium.org>