[16.0][FIX] Add ondelete=cascade to wizard item wiz_id fields

[dnplkndll]

Summary

Fix ForeignKeyViolation errors when ir.autovacuum cleans up transient wizard records.

Without ondelete="cascade" on the wiz_id field, deleting the parent wizard leaves orphan child items that still reference it, causing FK constraint violations:

ForeignKeyViolation: UPDATE or DELETE on table "rma_refund" violates foreign key constraint
"rma_refund_item_wiz_id_fkey" on table "rma_refund_item"
DETAIL: Key (id)=(123) is still referenced from table "rma_refund_item".

This follows the pattern from PR #489 (commit 03ecdff) which fixed the same issue for rma_make_picking_wizard_item.

Affected wizards

Module	TransientModel
rma_account	rma.refund.item
rma_purchase	rma.order.line.make.purchase.order.item
rma_sale	rma.order.line.make.sale.order.item
rma_put_away	rma_make_put_away_item.wizard
rma_scrap	rma_make_scrap_item.wizard

Test plan

• Pre-commit hooks pass
• Wait for ir.autovacuum cron to run and verify no FK errors in logs

[dnplkndll]

@JordiBForgeFlow @MiquelRForgeFlow