minor #21783 [DependencyInjection] remove dead code (hhamon)

This PR was merged into the 2.7 branch.

Discussion
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[DependencyInjection] remove dead code

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | ~
| License       | MIT
| Doc PR        | ~

This PR removes some dead code introduced 7 years ago (!!!) by a wrong merge :)

Commits
-------

158b689 [DependencyInjection] removed dead code.

src/Symfony/Component/DependencyInjection/Tests/Dumper/PhpDumperTest.php

@@ -34,13 +34,10 @@ public static function setUpBeforeClass()
 
     public function testDump()
     {
-        $dumper = new PhpDumper($container = new ContainerBuilder());
+        $dumper = new PhpDumper(new ContainerBuilder());
 
         $this->assertStringEqualsFile(self::$fixturesPath.'/php/services1.php', $dumper->dump(), '->dump() dumps an empty container as an empty PHP class');
         $this->assertStringEqualsFile(self::$fixturesPath.'/php/services1-1.php', $dumper->dump(array('class' => 'Container', 'base_class' => 'AbstractContainer', 'namespace' => 'Symfony\Component\DependencyInjection\Dump')), '->dump() takes a class and a base_class options');
-
-        $container = new ContainerBuilder();
-        new PhpDumper($container);
     }
 
     public function testDumpOptimizationString()