[Components][Config][Definition] Fix code sample

Author: iamdto

components/config/definition.rst

@@ -177,11 +177,12 @@ Or you may define a prototype for each node inside an array node::
         ->children()
             ->arrayNode('connections')
                 ->prototype('array')
-                ->children()
-                    ->scalarNode('driver')->end()
-                    ->scalarNode('host')->end()
-                    ->scalarNode('username')->end()
-                    ->scalarNode('password')->end()
+                    ->children()
+                        ->scalarNode('driver')->end()
+                        ->scalarNode('host')->end()
+                        ->scalarNode('username')->end()
+                        ->scalarNode('password')->end()
+                    ->end()
                 ->end()
             ->end()
         ->end()