OWNERS: update to include OWNERS.testplatform

Exempt-From-Owner-Approval: doesn't change the intent of the OWNERS
Change-Id: I76b8a348011d56d57261fc7d7bd658178fc8f0b0
diff --git a/OWNERS b/OWNERS
index 5138a5b..c9d5620 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1,7 +1,5 @@
+include chromiumos/chromite:/OWNERS.testplatform
+
 ayatane@chromium.org
-jkop@chromium.org
-linxinan@chromium.org
-pprabhu@chromium.org
 vivekshah@chromium.org
 xixuan@chromium.org
-zamorzaev@chromium.org