minor symfony#7859 Update options_resolver.rst (ZCJ)

This PR was submitted for the 3.2 branch but it was merged into the 2.7 branch instead (closes symfony#7859).

Discussion
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Update options_resolver.rst

clarify the comment

Commits
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8961f73 Update options_resolver.rst

Author: xabbuh

components/options_resolver.rst

@@ -98,7 +98,7 @@ the ``Mailer`` class makes a mistake?
 .. code-block:: php
 
     $mailer = new Mailer(array(
-        'usernme' => 'johndoe',  // usernAme misspelled
+        'usernme' => 'johndoe',  // usernme misspelled (instead of username)
     ));
 
 No error will be shown. In the best case, the bug will appear during testing,