fix: Remove non-current iceberg columns from catalog

[svdimchenko]

Description

Remove non-current iceberg columns from catalog

Models used to test - Optional

{{
    config(
        materialized="table",
        table_type="iceberg",
        post_hook="alter table model drop column to_drop"
    )
}}
select 1 as id, 'to_drop' as to_drop

Previously, dbt docs generate command generated catalog.json artifact which included to_drop column as well, however it did not exist in current table version.
Current PR fixes this behaviour and stores in catalog.json file only actual columns.

Checklist

• You followed contributing section
• You kept your Pull Request small and focused on a single feature or bug fix.
• You added unit testing when necessary
• You added functional testing when necessary

[nicor88]

Should fix #726

[nicor88]

@colin-rogers-dbt please have a look.