Add missing index renaming when completing a migration

[kvch]

During testing the faithful duplication of indexed columns I discovered that
if a column is included in multiple indices the only one of the indices are renamed. It happened because the index was deleted from the bookkeeper in the table even if the index was not renamed.

postgres=# \d items
                                          Table "public.items"
 Column |          Type          | Collation | Nullable |                    Default
--------+------------------------+-----------+----------+-----------------------------------------------
 id     | integer                |           | not null | nextval('_pgroll_new_items_id_seq'::regclass)
 city   | character varying(255) |           |          |
 name   | character varying(255) |           |          |
Indexes:
    "_pgroll_new_items_pkey" PRIMARY KEY, btree (id)
    "_pgroll_dup_idx_items_unique_name" UNIQUE, btree (name)
    "items_unique_name_id" UNIQUE CONSTRAINT, btree (city, name)

Correct output after my fix:

postgres=# \d items
                                          Table "public.items"
 Column |          Type          | Collation | Nullable |                    Default
--------+------------------------+-----------+----------+-----------------------------------------------
 id     | integer                |           | not null | nextval('_pgroll_new_items_id_seq'::regclass)
 city   | character varying(255) |           |          |
 name   | character varying(255) |           |          |
Indexes:
    "_pgroll_new_items_pkey" PRIMARY KEY, btree (id)
    "idx_items_unique_name" UNIQUE, btree (name)
    "items_unique_name_id" UNIQUE CONSTRAINT, btree (city, name)

[ryanslade]

Might be worth adding a test for this?