minor #19964 fixed a deprecation warning in tests (fabpot)

This PR was merged into the 3.2-dev branch.

Discussion
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fixed a deprecation warning in tests

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Commits
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9e1589e fixed a deprecation warning in tests

Author: nicolas-grekas

src/Symfony/Component/Validator/Tests/Constraints/ChoiceValidatorTest.php

@@ -142,7 +142,7 @@ public function testValidChoiceCallbackContextObjectMethod()
         // search $this for "objectMethodCallback"
         $this->setObject($this);
 
-        $constraint = new Choice(array('callback' => 'objectMethodCallback'));
+        $constraint = new Choice(array('callback' => 'objectMethodCallback', 'strict' => true));
 
         $this->validator->validate('bar', $constraint);