minor #4554 Changed url to PHP-CS-FIXER repository (jzawadzki)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #4554).

Discussion
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Changed url to PHP-CS-FIXER repository

I've updated php-cs-fixer links as it's moved to FriendsOfPHP

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

Commits
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332b6d4 Changed url to PHP-CS-FIXER repository

Author: wouterj

best_practices/business-logic.rst

@@ -339,4 +339,4 @@ in a matter of seconds.
 .. _`PSR-1`: http://www.php-fig.org/psr/psr-1/
 .. _`PSR-2`: http://www.php-fig.org/psr/psr-2/
 .. _`the Symfony Code Standards`: http://symfony.com/doc/current/contributing/code/standards.html
-.. _`PHP-CS-Fixer`: https://github.com/fabpot/PHP-CS-Fixer
+.. _`PHP-CS-Fixer`: https://github.com/FriendsOfPHP/PHP-CS-Fixer