Storage Monitor: Add tommycli to OWNERS, remove emeritus OWNERS.

Removes people no longer on Chromium team.

Bug: NONE
Change-Id: Ib710dae406e9691ff7abb33e8faad0ffff13dd06
Reviewed-on: https://chromium-review.googlesource.com/576141Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#487520}

components/storage_monitor/OWNERS

 thestig@chromium.org
-vandebo@chromium.org
-gbillock@chromium.org
+tommycli@chromium.org