[12.0][FIX] account_asset_management: fix error in parent to group migration

Return the id from the subselect by its column name in the main query. Fixes
incomplete and incorrect group assignment during the migration.

account_asset_management/migrations/12.0.2.0.0/post-migration.py

@@ -28,7 +28,7 @@ def create_asset_groups(cr):
         LEFT JOIN account_asset_group aag2
             ON aag2.{origin_column} = va.{parent_column}
         WHERE {parent_column} {rest_sql}
-        RETURNING id
+        RETURNING {origin_column}
     """)
     isnull = sql.SQL("IS NULL")
     inids = sql.SQL("IN %(ids)s")