Remove davidben and mmenke from prerender OWNERS.

We have not worked on this code for years. Others have more context around it
these days.

Bug: none
Change-Id: I95c258b08b6e25c359b3b7faa6bfa91cede95350
Reviewed-on: https://chromium-review.googlesource.com/1186981
Commit-Queue: David Benjamin <davidben@chromium.org>
Reviewed-by: Egor Pasko <pasko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585512}

chrome/browser/prerender/OWNERS

-davidben@chromium.org
 droger@chromium.org
 mattcary@chromium.org
-mmenke@chromium.org
 pasko@chromium.org
 
 # COMPONENT: Internals>Preload