minor correction to external_source.sql

deployment/postgres-init-db/sql/tables/merlin/external_events/external_source.sql

@@ -99,7 +99,7 @@ create function merlin.external_source_pdg_ack_update()
   returns trigger
   language plpgsql as $$
 begin
-  update merlin.plan_derivation_group set 'acknowledged' = false
+  update merlin.plan_derivation_group set plan_derivation_group.acknowledged = false
   where plan_derivation_group.derivation_group_name = NEW.derivation_group_name;
   return new;
 end;