Fix invoicing SQL (#824)

core/src/test/resources/google/registry/beam/invoicing/billing_events_test.sql

@@ -55,7 +55,7 @@ FROM (
     FROM
       `my-project-id.latest_datastore_export.Registry`
     WHERE
-      enableInvoicing IS TRUE) ) AS BillingEvent
+      invoicingEnabled IS TRUE) ) AS BillingEvent
   -- Gather billing ID from registrar table
   -- This is a 'JOIN' as opposed to 'LEFT JOIN' to filter out
   -- non-billable registrars