GitLab

Removes the old 2016 system health stories that have been updated
to 2018/9 recordings.

Perf Sheriffs: This change will cause movement in metrics which track
across the whole story set instead of individual stories.

BUG=chromium:878390

Change-Id: I3504263c8f432fe6a26336f45d56775e08cd579a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2012954
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735368}