AC-6057: Fixed minor Unit Test issue

Author: nishant04412

app/code/Magento/Quote/Test/Unit/Model/QuoteManagementTest.php

@@ -197,6 +197,11 @@ class QuoteManagementTest extends TestCase
      */
     private $quoteIdMaskFactoryMock;
 
+    /**
+     * @var LockManagerInterface|MockObject
+     */
+    private $lockManagerMock;
+
     /**
      * @inheriDoc
      *