minor #28349 Fix usage of setUp in tests (4.1) (fabpot)

This PR was merged into the 4.1 branch.

Discussion
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Fix usage of setUp in tests (4.1)

| Q             | A
| ------------- | ---
| Branch?       | 4.1
| Bug fix?      | no
| New feature?  | no <!-- don't forget to update src/**/CHANGELOG.md files -->
| BC breaks?    | no     <!-- see https://symfony.com/bc -->
| Deprecations? | no <!-- don't forget to update UPGRADE-*.md and src/**/CHANGELOG.md files -->
| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->
| License       | MIT

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Commits
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d8ba2cd703 fixed usage of setUp in tests

src/Symfony/Component/DependencyInjection/Tests/ParameterBag/ContainerBagTest.php

@@ -26,7 +26,7 @@ class ContainerBagTest extends TestCase
     /** @var ContainerBag */
     private $containerBag;
 
-    public function setUp()
+    protected function setUp()
     {
         $this->parameterBag = new ParameterBag(array('foo' => 'value'));
         $this->containerBag = new ContainerBag(new Container($this->parameterBag));