Fix example with iterable

Author: peterjaap

components/console/helpers/progressbar.rst

@@ -110,11 +110,17 @@ which starts, advances and finishes the progress bar automatically::
 
     $progressBar = new ProgressBar($output);
 
-    // $iterable can be for example an array ([1, 2, 3, ...]) or a generator
-    // $iterable = function () { yield 1; yield 2; ... };
+    // $iterable can be for example an array ([1, 2, 3, ...])
+    $iterable = [1, 2];
     foreach ($progressBar->iterate($iterable) as $value) {
         // ... do some work
     }
+    
+    // or a generator
+    function iterable() { yield 1; yield 2; ... };
+    foreach ($progressBar->iterate(iterable()) as $value) {
+        // ... do some work
+    }
 
 If ``$iterable = [1, 2]``, the previous code will output the following: