Replace with a saner example

Author: paulbalandan

user_guide_src/source/testing/benchmark/007.php

@@ -2,12 +2,6 @@
 
 $iterator = new \CodeIgniter\Debug\Iterator();
 
-// Add a new task
-$iterator->add('single_concat', static function () {
-    $str = 'Some basiclittlestring concatenation test.';
-});
-
-// Add another task
-$iterator->add('double', static function ($a = 'little') {
-    $str = "Some basic {$little} string test.";
+$iterator->add('double', static function ($word = 'little') {
+    "Some basic {$word} string test.";
 });