strip internal spaces in HTS number

The WPINT API requires a 10-digit HTS number without any spaces,
while the source number may contain spaces.  Our use of 'strip()' is
insufficient as it only removes leading and trailing spaces, but not
spaces inside the number.  We need to do replace(' ', '') instead.

Related: SYS#5415

models/dp_delivery_carrier.py

@@ -152,7 +152,7 @@ class DPDeliveryCarrier(models.Model):
             else:
                 raise Warning('Product %s has no Country of Origin defined' % (ptempl.name))
             weight = ptempl.weight
-        hts = ptmpl.customs_code.strip()
+        hts = ptmpl.customs_code.replace(' ', '')
         desc = ptmpl.customs_description_en
         if line.procurement_id and line.procurement_id.sale_line_id:
             price_unit = line.procurement_id.sale_line_id.price_unit