bug #6761 fixed missing level in namespace (themasch)

This PR was submitted for the 3.1 branch but it was merged into the 2.8 branch instead (closes #6761).

Discussion
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fixed missing level in namespace

The link to the UserCheckerInterface seems to be wrong.

Commits
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8d60d5c fixed missing level in namespace

Author: weaverryan

security/user_checkers.rst

@@ -16,7 +16,7 @@ Creating a Custom User Checker
 ------------------------------
 
 User checkers are classes that must implement the
-:class:`Symfony\\Component\\Security\\Core\\UserCheckerInterface`. This interface
+:class:`Symfony\\Component\\Security\\Core\\User\\UserCheckerInterface`. This interface
 defines two methods called ``checkPreAuth()`` and ``checkPostAuth()`` to
 perform checks before and after user authentication. If one or more conditions
 are not met, an exception should be thrown which extends the