Remove rockot@ from extensions OWNERS

I've left myself in OWNERS of some specific device APIs just to share
the load with other owners there, but it seems like there is diminishing
value in having me own the broader extensions/ dir given my waning
familiarity with the system.

Bug: None
Change-Id: I502d6ae4f61ba9b5cadf1bdc083b53d6160b9891
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2210624
Auto-Submit: Ken Rockot <rockot@google.com>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#770742}

extensions/OWNERS

@@ -14,7 +14,6 @@ lazyboy@chromium.org
 karandeepb@chromium.org
 dbertoni@chromium.org
 benwells@chromium.org
-rockot@google.com
 finnur@chromium.org
 reillyg@chromium.org
 

extensions/browser/OWNERS

 # Please talk to the apps shell team before adding DEPS.
 per-file DEPS=benwells@chromium.org
-per-file DEPS=rockot@google.com
 per-file DEPS=rdevlin.cronin@chromium.org
 
 per-file extension_event_histogram_value.h=set noparent