Prerender: update OWNERS

Remove droger@ who is no longer on the team, and add lizeb@ to
keep a minimum of three people involved.

Change-Id: Ic6f28a106a679058dc74d65afc07475edbe251c8
TBR: pasko@chromium.org,lizeb@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/c/1335467Reviewed-by: Matthew Cary <mattcary@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Matthew Cary <mattcary@chromium.org>
Cr-Commit-Position: refs/heads/master@{#607940}

chrome/browser/prerender/OWNERS

-droger@chromium.org
+lizeb@chromium.org
 mattcary@chromium.org
 pasko@chromium.org