Remove customer tax id required for Poland

Author: mrdanwa

addons/pl/favat/bill.go

@@ -72,9 +72,6 @@ func billInvoiceRules() *rules.Set {
 		rules.When(is.Func("not simplified", invoiceNotSimplified),
 			rules.Field("customer",
 				rules.Assert("09", "customer is required", is.Present),
-				rules.Field("tax_id",
-					rules.Assert("10", "customer tax ID is required", is.Present),
-				),
 			),
 		),
 		// Customer JST identity check (invoice-level, needs both customer.ext and customer.identities)