minor #5646 Moved comment to the right place (mickaelandrieu)

This PR was submitted for the 2.7 branch but it was merged into the 2.3 branch instead (closes #5646).

Discussion
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Moved comment to the right place

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | >= 2.3 afaik
| Fixed tickets | none

I think this move is required because we can think at this moment that the function ``link()`` send the click that is wrong (link() function create a Link object from the selector or throw an exception).

Commits
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9353afc Moved comment to the right place

Author: xabbuh

book/testing.rst

@@ -196,9 +196,10 @@ expression or a CSS selector, then use the client to click on it. For example::
     $link = $crawler
         ->filter('a:contains("Greet")') // find all links with the text "Greet"
         ->eq(1) // select the second link in the list
-        ->link() // and click it
+        ->link()
     ;
-
+    
+    // and click it
     $crawler = $client->click($link);
 
 Submitting a form is very similar: select a form button, optionally override