Documentation should refers to @Security and no @Secure

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | yes
| Applies to    | 2.4+
| Fixed tickets | none

The @Security annotation is only documented on the FrameworkExtraBundle documentation, which is not the first place when we search informations about security.

I think the Security part of the official documentation should refers to this new annotation which is available with the standart edition of Symfony 2 instead of third libraries.