fix error with phpunit10 (security_helper_test class not found)

 1) Class security_helper_test cannot be found in tests/codeigniter/helpers/security_helper_test.php

Author: tenzap

tests/codeigniter/helpers/security_helper_test.php

@@ -1,8 +1,8 @@
 <?php
 
-class Security_helper_tests extends CI_TestCase {
+class Security_helper_test extends CI_TestCase {
 
-	function setUp()
+	function set_up()
 	{
 		$this->helper('security');
 		$obj = new stdClass;