fix: insert_overwrite updates for tables with int partitions

[artem-garmash]

Description

Fix incremental updates for tables with the insert_overwrite strategy and int partition columns when using dbt-core==1.6.3. Otherwise updates fail with:

  can only concatenate str (not "NoneType") to str
  
  > in macro materialization_incremental_athena (macros/materializations/models/incremental/incremental.sql)
  > called by ...

The root cause is exactly as in #425 (convert_type() returns None for int columns)
This PR adds the same workaround to delete_overlapping_partitions().

Models used to test - Optional

{{
	config(
		materialized = 'incremental',
		incremental_strategy = 'insert_overwrite',
		partitioned_by = ['m']
	)
}}

select 'val' as val, 1 as m

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