Merge branch '6.4' into 7.0

* 6.4:
  Update contributing/code/tests.rst page

Author: javiereguiluz

contributing/code/tests.rst

@@ -32,7 +32,7 @@ tests, such as Doctrine, Twig and Monolog. To do so,
 
     .. code-block:: terminal
 
-        $ COMPOSER_ROOT_VERSION=5.4.x-dev composer update
+        $ COMPOSER_ROOT_VERSION=6.4.x-dev composer update
 
 .. _running: