Add falken and nhiroki to prerender owners

Change-Id: I9e7db8e9775b9e6cd0813ffeaad68405bcc96607
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2487946Reviewed-by: Robert Ogden <robertogden@chromium.org>
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Reviewed-by: Matt Falkenhagen <falken@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#819185}

components/prerender/OWNERS

+falken@chromium.org
+nhiroki@chromium.org
 robertogden@chromium.org
 ryansturm@chromium.org
 tbansal@chromium.org