[ONC] Update //components/onc/OWNERS

Adds ChromeOS connectivity team members to owners for //components/onc

Bug: 1231305
Change-Id: I4052659b45b6baf95f067ae70c38f933ba0ca6ad
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3058040


Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Commit-Queue: Azeem Arshad <azeemarshad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#908681}