Add eugenebut@ and gambard@ as ios/web/browsing_data/OWNERS.

gambard@ was initial author and eugenebut@ was a reviewer of this code.

Bug: None
Change-Id: Ibf65061c43e10af2b6930b2363e022aa6807f4e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1664518
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Auto-Submit: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#670453}