minor symfony#9328 Markup in Config Validation example (ProgMiner)

This PR was merged into the 4.0 branch.

Discussion
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Markup in Config Validation example

With the previous markup, it is intuitively unclear what `->end()` is applied to `->validate()`.

Commits
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d823cbf Markup in validation example

Author: javiereguiluz

components/config/definition.rst

@@ -726,7 +726,7 @@ The builder is used for adding advanced validation rules to node definitions, li
                     ->scalarNode('driver')
                         ->isRequired()
                         ->validate()
-                        ->ifNotInArray(array('mysql', 'sqlite', 'mssql'))
+                            ->ifNotInArray(array('mysql', 'sqlite', 'mssql'))
                             ->thenInvalid('Invalid database driver %s')
                         ->end()
                     ->end()