Remove noparent for build/config/BUILDCONFIG.gn

The GN build is established enough by now that regular hierarchical owner
hierarchies should be enough.

Bug: none
Change-Id: I742de174a6c2a27de09931b8c5a403619d62ff2a
Reviewed-on: https://chromium-review.googlesource.com/c/1388725
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#618575}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 8a74e576388de386ba81e59b199fe9efdcd8cc3b

config/OWNERS

@@ -2,6 +2,3 @@ dpranke@chromium.org
 scottmg@chromium.org
 
 per-file *jumbo*=bratell@opera.com
-
-per-file BUILDCONFIG.gn=dpranke@chromium.org
-per-file BUILDCONFIG.gn=set noparent