Remove eugenebut from ios/chrome/browser/u2f owners

Bug: None
Change-Id: I05dce85f55787d5b20399eed88feb0abf8c09523
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2633849
Auto-Submit: Eugene But <eugenebut@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844479}

ios/chrome/browser/u2f/OWNERS

-eugenebut@chromium.org