minor #12447 Update validation.rst (atailouloute)

This PR was merged into the 3.4 branch.

Discussion
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Update validation.rst

As the Validator class does not exist anymore, this part is not up to date.

Commits
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0bb5b5b Update validation.rst

Author: javiereguiluz

validation.rst

@@ -111,7 +111,7 @@ Using the ``validator`` Service
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 Next, to actually validate an ``Author`` object, use the ``validate()`` method
-on the ``validator`` service (class :class:`Symfony\\Component\\Validator\\Validator`).
+on the ``validator`` service (implementation of :class:`Symfony\\Component\\Validator\\Validator\\ValidatorInterface`).
 The job of the ``validator`` is easy: to read the constraints (i.e. rules)
 of a class and verify if the data on the object satisfies those
 constraints. If validation fails, a non-empty list of errors