TBR: Fix perms.WriteTo in mojo_impl.

Required by v.io/c/14484

Change-Id: Ie382f9580719e676b7454266a413e2d77fb9e8d0
diff --git a/x/ref/services/syncbase/server/mojo_impl.go b/x/ref/services/syncbase/server/mojo_impl.go
index fe515f1..52e2d90 100644
--- a/x/ref/services/syncbase/server/mojo_impl.go
+++ b/x/ref/services/syncbase/server/mojo_impl.go
@@ -73,7 +73,7 @@
 
 func toMojoPerms(vPerms access.Permissions) (mojom.Perms, error) {
 	b := new(bytes.Buffer)
-	if err := vPerms.WriteTo(b); err != nil {
+	if err := access.WritePermissions(b, vPerms); err != nil {
 		return mojom.Perms{}, err
 	}
 	return mojom.Perms{Json: b.String()}, nil