minor #16982 Fix broken reference to CommandCompletionTester class (arogachev)

This PR was squashed before being merged into the 5.4 branch.

Discussion
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Fix broken reference to CommandCompletionTester class

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Commits
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a9ff660 Fix broken reference to CommandCompletionTester class

Author: javiereguiluz

console/input.rst

@@ -368,7 +368,7 @@ Testing the Completion script
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 The Console component comes with a special
-:class:`Symfony\\Component\\Console\\Test\\CommandCompletionTester`` class
+:class:`Symfony\\Component\\Console\\Tester\\CommandCompletionTester`` class
 to help you unit test the completion logic::
 
     // ...