Failed to undistribute table on generated primary key column

Given following table, Citus is able to create distributed table but failed to revert into undistributed one.

```
create table gis.address
(
address_id bigint generated always as identity (minvalue 1000000000)
constraint address_pk
primary key,
place_geom geometry(Point, 4326),
query_name text,
place_name text,
place_address text
);

alter table gis.address
owner to postgres;

create index address_address_id_index
on gis.address (address_id);

create index address_query_name_index
on gis.address (query_name);

```

SELECT create_distributed_table('gis.address', 'address_id'); -- SUCCESS
SELECT undistribute_table('gis.address'); -- FAILED
-- [0A000] ERROR: cannot complete operation on a table with identity column