Remove eugenebut from ios/chrome/browser/store_kit owners

Bug: None
Change-Id: I7a65f31b28c977a92c8d96759d29f35bc364a237
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2634268
Auto-Submit: Eugene But <eugenebut@chromium.org>
Reviewed-by: Mohammad Refaat <mrefaat@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845338}

ios/chrome/browser/store_kit/OWNERS

-eugenebut@chromium.org
 mrefaat@chromium.org