bug symfony#6915 Fix the error in code example (kruglikov)

This PR was submitted for the 3.1 branch but it was merged into the 2.7 branch instead (closes symfony#6915).

Discussion
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Fix the error in code example

Commits
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3f6fce9 Fix the error in code example

Author: wouterj

configuration.rst

@@ -244,7 +244,7 @@ key:
         $container->setParameter('locale', 'en');
 
         $container->loadFromExtension('framework', array(
-            'default_locale' => '%en%',
+            'default_locale' => '%locale%',
             // ...
         ));