store-db: disable autovacuum by default

The bigger table, messages, is a partitioned one where only INSERTS
happens. Furthermore, there are no dead tuples there because we
directly drop old partitions

We may need to manually perform vacuum on other tables

ansible/group_vars/store-db.yml

@@ -55,6 +55,8 @@ postgres_system_setting_stage:
     max_parallel_workers_per_gather: '2'
     max_parallel_workers: '4'
     max_parallel_maintenance_workers: '2'
+  ## Autovacuum
+  autovacuum: 'off'
 
 # Consul
 postgres_ha_consul_check_interval: '60s'