Small code adjustments

Author: eduard13

dev/tests/integration/testsuite/Magento/Checkout/Controller/Cart/Index/CouponPostTest.php

@@ -6,6 +6,8 @@
 
 namespace Magento\Checkout\Controller\Cart\Index;
 
+use Magento\Framework\App\Request\Http as HttpRequest;
+
 /**
  * @magentoDbIsolation enabled
  */
@@ -44,7 +46,7 @@ public function testExecute()
      * @magentoDataFixture Magento/Usps/Fixtures/cart_rule_coupon_free_shipping.php
      * @return void
      */
-    public function testAddingValidCoupon(): void
+    public function testAddingValidCoupon()
     {
         /** @var $session \Magento\Checkout\Model\Session */
         $session = $this->_objectManager->create(\Magento\Checkout\Model\Session::class);
@@ -63,7 +65,7 @@ public function testAddingValidCoupon(): void
         );
 
         $this->assertSessionMessages(
-            $this->equalTo(['You used coupon code "' . $couponCode . '".']),
+            $this->equalTo(['You used coupon code "' . $couponCode . '".']),
             \Magento\Framework\Message\MessageInterface::TYPE_SUCCESS
         );
     }