minor #17011 [CONSOLE] Remove unnecessary test (krzysiekpiasecki)

This PR was submitted for the 3.0 branch but it was merged into the 2.7 branch instead (closes #17011).

Discussion
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[CONSOLE] Remove unnecessary test

Question interface 'quarantees'  that $validator is null or callable

Commits
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5dc9bd9 Remove unnecessary test

src/Symfony/Component/Console/Helper/SymfonyQuestionHelper.php

@@ -32,7 +32,7 @@ class SymfonyQuestionHelper extends QuestionHelper
     {
         $validator = $question->getValidator();
         $question->setValidator(function ($value) use ($validator) {
-            if (null !== $validator && is_callable($validator)) {
+            if (null !== $validator) {
                 $value = $validator($value);
             }