Make typed property for ResponseTraitTest

Author: samsonasik

tests/system/API/ResponseTraitTest.php

@@ -29,16 +29,8 @@
  */
 final class ResponseTraitTest extends CIUnitTestCase
 {
-    /**
-     * @var MockIncomingRequest|null
-     */
-    private $request;
-
-    /**
-     * @var MockResponse|null
-     */
-    private $response;
-
+    private ?MockIncomingRequest $request  = null;
+    private ?MockResponse $response        = null;
     private ?FormatterInterface $formatter = null;
 
     protected function setUp(): void