bug #5358 Fix typo in description (martyshka)

This PR was submitted for the 2.7 branch but it was merged into the 2.6 branch instead (closes #5358).

Discussion
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Fix typo in description

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.7
| Fixed tickets |

Commits
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8a0a995 Fix typo in description

cookbook/security/api_key_authentication.rst

@@ -634,7 +634,7 @@ current URL is before creating the token in ``createToken()``::
 This uses the handy :class:`Symfony\\Component\\Security\\Http\\HttpUtils`
 class to check if the current URL matches the URL you're looking for. In this
 case, the URL (``/login/check``) has been hardcoded in the class, but you
-could also inject it as the third constructor argument.
+could also inject it as the second constructor argument.
 
 Next, just update your service configuration to inject the ``security.http_utils``
 service: