libmetrics: remove version 180609

BUG=chromium:361748
CQ-DEPEND=CL:195565
CQ-DEPEND=CL:195570
CQ-DEPEND=CL:195548
TEST=Trybot runs on paladin, release and chromiumos-sdk builders.

Change-Id: I09fdbdad6752ced19bc0dc6cfecdc67f1867c2cf
Reviewed-on: https://chromium-review.googlesource.com/195580


Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Ben Chan <benchan@chromium.org>