Remove eugenebut from ios/web_view owners

Bug: None
Change-Id: I9463f5c2717d5e5227d8873129fbd5a78e07afc8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2633966
Auto-Submit: Eugene But <eugenebut@chromium.org>
Commit-Queue: John Wu <jzw@chromium.org>
Reviewed-by: John Wu <jzw@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844426}

ios/web_view/OWNERS

-eugenebut@chromium.org
 ichikawa@chromium.org
 jzw@chromium.org
 michaeldo@chromium.org