Add more OWNERS to OTS

We need additional people be able to roll / update OTS.

Bug: 1158389
Change-Id: I0cea226158183545e8bc4b06aca2f21ff088a68d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2590037Reviewed-by: Ben Wagner <bungeman@chromium.org>
Reviewed-by: Kenichi Ishibashi <bashi@chromium.org>
Commit-Queue: Kenichi Ishibashi <bashi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#836685}

third_party/ots/OWNERS

 bashi@chromium.org
+bungeman@chromium.org
 jshin@chromium.org
+kojii@chromium.org