[FIX] sale: delete draft invoices with downpayments

Create a SO, Validate it.
Create Invoice: down payment (fixed amount) and validate invoice
Now back to the SO. Create Invoice: Invoiceable lines (deduct down payments).
A draft invoice is created. Try to delete it.

User gets an error, this occur because the second invoice creation bind
another invoice_line to the downpayment sale order line (first line was
added when making the downpayment). When the user delete the invoice
the sale order line should be deleted as well, but is still linked to an
invoice so the error raise.
Unlinking only unbinded sol fix the issue

opw-2258218

closes odoo/odoo#53144

X-original-commit: 7c7275b8a943196975182a8e66cef0e82f87b21d
Signed-off-by: Nicolas Martinelli (nim) <nim@odoo.com>

addons/sale/models/account_invoice.py

@@ -36,7 +36,7 @@ class AccountMove(models.Model):
             self.fiscal_position_id = fiscal_position
 
     def unlink(self):
-        downpayment_lines = self.mapped('line_ids.sale_line_ids').filtered(lambda line: line.is_downpayment)
+        downpayment_lines = self.mapped('line_ids.sale_line_ids').filtered(lambda line: line.is_downpayment and line.invoice_lines <= self.mapped('line_ids'))
         res = super(AccountMove, self).unlink()
         if downpayment_lines:
             downpayment_lines.unlink()