[iOS] Removing bzanotti from ios/chrome/browser/signin/OWNERS

Removing bzanotti from ios/chrome/browser/signin/OWNERS.

Change-Id: Ie50fefddfa33e0b178b94d2e3eb08536ce803933
Reviewed-on: https://chromium-review.googlesource.com/c/1355123Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612194}

ios/chrome/browser/signin/OWNERS

-bzanotti@chromium.org
 jlebel@chromium.org
 msarda@chromium.org