Fix broken link on Community docs page

doc/07-community.md

@@ -19,8 +19,7 @@ The most important guidelines are described as follows:
 > Fork the project, create a feature branch, and send us a pull request.
 >
 > To ensure a consistent code base, you should make sure the code follows
-> the [Coding Standards](https://symfony.com/doc/2.0/contributing/code/standards.html)
-> which we borrowed from Symfony.
+> the [PSR-2 Coding Standards](http://www.php-fig.org/psr/psr-2/).
 
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