fixed a test: removed a function call which does not exist (yet)

Author: Hevesi Gergő

tests/Write/ExtensionTest.php

@@ -185,7 +185,6 @@ public function testIfXMLIsValid()
             ->setId(1234)
             ->setCopyIndicator(false)
             ->setIssueDate(new \DateTime())
-            ->setIssueTime(new \DateTime())
             ->setAccountingSupplierParty($accountingSupplierParty)
             ->setAccountingCustomerParty($accountingCustomerParty)
             ->setInvoiceLines($invoiceLines)