Remove extensions/browser/api OWNERS file

I'm the only person in the list, and given that I'm not actively working
on apps APIs, it's probably not worth having me as an owner for all api
implementations any longer. (Lately, I've been just redirecting all review
requests).

Change-Id: Ib3f09a12ae2cfde6004e657368229fb2be662165
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1856840
Auto-Submit: Toni Baržić <tbarzic@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705248}

chrome/browser/extensions/api/OWNERS

-# For Chrome OS apps APIs.
-tbarzic@chromium.org

extensions/browser/api/OWNERS

-# For Chrome OS apps APIs.
-tbarzic@chromium.org
-# COMPONENT: Platform>Extensions>API