Use native function instead of Zend_Mime_Decode::decodeQuotedPrintable()

Author: Ben Batschelet

dev/tests/integration/testsuite/Magento/Wishlist/Controller/IndexTest.php

@@ -169,9 +169,7 @@ public function testSendAction()
             \Magento\TestFramework\Mail\Template\TransportBuilderMock::class
         );
 
-        $actualResult = \Zend_Mime_Decode::decodeQuotedPrintable(
-            $transportBuilder->getSentMessage()->getRawMessage()
-        );
+        $actualResult = quoted_printable_decode($transportBuilder->getSentMessage()->getRawMessage());
 
         $this->assertStringMatchesFormat(
             '%A' . $this->_customerViewHelper->getCustomerName($this->_customerSession->getCustomerDataObject())