Don't allow plugin owners to push without review

This should make it more difficult to bypass review by mistake. We
still allow self-review so owners can still make progress unilaterally
in an emergency if they need to.

Change-Id: I740745dae8a0c2025b3a665d0a7cee429a287266
diff --git a/project.config b/project.config
index b1dae7d..9c75f45 100644
--- a/project.config
+++ b/project.config
@@ -4,7 +4,6 @@
 	description = Parent project for plugins/*
 [access "refs/heads/*"]
 	create = group Project Owners
-	push = group Project Owners
 	label-Code-Review = -2..+2 group Project Owners
 	label-Verified = -1..+1 group Change Owner
 	label-Verified = -1..+1 group Project Owners