Cleanup heap/ OWNERS

Change-Id: Ie060c1a6e9cac18c8366e89235961917f0e4b146
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1862927
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706000}

third_party/blink/renderer/platform/heap/OWNERS

 bikineev@chromium.org
-erik.corry@gmail.com
 haraken@chromium.org
 kouhei@chromium.org
 mlippautz@chromium.org