Allow Gerrit to subscribe to its plugins

Change-Id: I0abfe4757c1b719633914a566fd5f39383247462
diff --git a/project.config b/project.config
index 7fe3d62..79f43ce 100644
--- a/project.config
+++ b/project.config
@@ -23,3 +23,5 @@
 [access "refs/for/refs/meta/config"]
 	push = group Registered Users
 	pushMerge = group Registered Users
+[allowSuperproject "gerrit"]
+	refs = refs/heads/*:refs/heads/*