Add vasilii@ to //ios/chrome/browser/passwords/OWNERS

Vasilii is the password manager team's expert on Objective C, knows password
manager code thoroughly and has experience in iOS codebase as well. An ideal
//ios/chrome/browser/passwords/OWNERS.

Bug: None
Change-Id: I5725b9da385fd73d97e71e8b9368841da3974130
Reviewed-on: https://chromium-review.googlesource.com/571224Reviewed-by: Vasilii Sukhanov <vasilii@chromium.org>
Commit-Queue: Vaclav Brozek <vabr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486751}

ios/chrome/browser/passwords/OWNERS

-vabr@chromium.org
 melandory@chromium.org
+vabr@chromium.org
+vasilii@chromium.org