Removing coordinator with citus local tables gives wrong error message

```sql
SELECT citus_add_node('localhost', 9701);
SELECT citus_add_node('localhost', 9700, 0);

create table reference_table(a int unique);
SELECT create_reference_table('reference_table');

-- new feature! :)
create table local_table(a int references reference_table(a));

table pg_dist_partition;
┌─────────────────┬────────────┬─────────┬──────────────┬──────────┐
│ logicalrelid │ partmethod │ partkey │ colocationid │ repmodel │
├─────────────────┼────────────┼─────────┼──────────────┼──────────┤
│ reference_table │ n │ │ 1 │ t │
│ local_table │ n │ │ 0 │ c │
└─────────────────┴────────────┴─────────┴──────────────┴──────────┘
(2 rows)

SELECT citus_remove_node('localhost', 9700);
```

ERROR: cannot remove the **last worker node** because there are reference tables and it would cause data loss on reference tables