project.config: Deny Blocked Users push access

Deny refs/for/refs to try to block spam changes.

Change-Id: I08bda79acb3fc1f67137d10d7260eac66e8afe56

project.config

diff --git a/project.config b/project.config
index 374b6ae..97429e2 100644
--- a/project.config
+++ b/project.config
@@ -16,6 +16,7 @@
 	revert = group aom-committers
 	revert = group aom-interns
 [access "refs/for/refs/*"]
+	push = deny group Blocked Users
 	push = group Registered Users
 [access "refs/heads/*"]
 	create = group Administrators