Adds sczs@ as ios/c/b/ui/ntp OWNER

The NTP refactoring will move quite a lot of code from content_suggestionswhere I'm already an Owner. Also, this way I'll be able to reviews these
changes.

Bug: 1114792
Change-Id: Ie82ea0525aafcb6c87c2c1a4bd9cce1188e238e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2570089
Auto-Submit: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833306}

ios/chrome/browser/ui/ntp/OWNERS

 rohitrao@chromium.org
 justincohen@chromium.org
 gambard@chromium.org
+sczs@chromium.org