Fix typo with the BackendTemplateTest serializerMock object

Author: dmanners

app/code/Magento/Email/Test/Unit/Model/BackendTemplateTest.php

@@ -46,7 +46,7 @@ class BackendTemplateTest extends \PHPUnit_Framework_TestCase
     /**
      * @var \Magento\Framework\Serialize\Serializer\Json|\PHPUnit_Framework_MockObject_MockObject
      */
-    private $serilizerMock;
+    private $serializerMock;
 
     protected function setUp()
     {
@@ -75,14 +75,14 @@ protected function setUp()
 
         \Magento\Framework\App\ObjectManager::setInstance($objectManagerMock);
 
-        $this->serilizerMock = $this->getMockBuilder(\Magento\Framework\Serialize\Serializer\Json::class)->getMock();
+        $this->serializerMock = $this->getMockBuilder(\Magento\Framework\Serialize\Serializer\Json::class)->getMock();
 
         $this->model = $helper->getObject(
             \Magento\Email\Model\BackendTemplate::class,
             [
                 'scopeConfig' => $this->scopeConfigMock,
                 'structure' => $this->structureMock,
-                'serializer' => $this->serilizerMock
+                'serializer' => $this->serializerMock
             ]
         );
     }