Remove owners rules for SmokeTests.

At this point there seems to be little danger that people will add
lines to SmokeTests willy-nilly, so I don't think we need special
owners for it.

R=ojan@chromium.org, jbudorick@chromium.org, peter@chromium.org

Change-Id: I75a71b1ee800348742177caf3ea94b1aca675d8b
Reviewed-on: https://chromium-review.googlesource.com/541603Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Ojan Vafai <ojan@chromium.org>
Reviewed-by: Peter Beverloo <peter@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#481016}

third_party/WebKit/LayoutTests/OWNERS

 *
 
-# Changes to the SmokeTests file must be actually approved so it doesn't grow willy-nilly.
-per-file SmokeTests=set noparent
-per-file SmokeTests=dpranke@chromium.org
-per-file SmokeTests=peter@chromium.org
-per-file SmokeTests=ojan@chromium.org
-
 per-file ImageFirstTests=set noparent
 per-file ImageFirstTests=file://third_party/WebKit/Source/core/layout/OWNERS