AC-15049 : [CE] PHPUnit 12: Upgrade Security & Authentication related test cases

Author: shashi011

app/code/Magento/User/Test/Unit/Controller/Adminhtml/User/SaveTest.php

@@ -16,7 +16,6 @@
 use Magento\Framework\ObjectManagerInterface;
 use Magento\Framework\Registry;
 use Magento\Framework\TestFramework\Unit\Helper\MockCreationTrait;
-use Magento\Framework\TestFramework\Unit\Helper\ObjectManager as ObjectManagerHelper;
 use Magento\User\Controller\Adminhtml\User\Save;
 use Magento\User\Model\User;
 use Magento\User\Model\UserFactory;