minor #16147 [VarDumper] consistent signature of getDump() in class + trait (xabbuh)

This PR was merged into the 2.8 branch.

Discussion
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[VarDumper] consistent signature of getDump() in class + trait

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #16126
| License       | MIT
| Doc PR        |

Commits
-------

48a9e83 consistent signature of getDump() in class + trait

src/Symfony/Component/VarDumper/Test/VarDumperTestCase.php

@@ -29,7 +29,7 @@ abstract class VarDumperTestCase extends \PHPUnit_Framework_TestCase
         $this->assertStringMatchesFormat(rtrim($dump), $this->getDump($data), $message);
     }
 
-    private function getDump($data)
+    protected function getDump($data)
     {
         $h = fopen('php://memory', 'r+b');
         $cloner = new VarCloner();

src/Symfony/Component/VarDumper/Test/VarDumperTestTrait.php

@@ -29,7 +29,7 @@ trait VarDumperTestTrait
         $this->assertStringMatchesFormat(rtrim($dump), $this->getDump($data), $message);
     }
 
-    public function getDump($data)
+    protected function getDump($data)
     {
         $h = fopen('php://memory', 'r+b');
         $cloner = new VarCloner();