minor symfony#17104 [Routing] Reduce memory usage of a high consuming test case (nicolas-grekas)

This PR was merged into the 2.3 branch.

Discussion
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[Routing] Reduce memory usage of a high consuming test case

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

Tests fail transiently on hhvm because of the high memory usage of this test case.
This patch cuts it by two.

See this blackfire comparison graph on the Memory dimension:
https://blackfire.io/profiles/compare/fd72ee66-e4d0-4ac2-92bf-16dd3849ef4c/graph?settings%5Bdimension%5D=pmu

Commits
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478a031 [Routing] Reduce memory usage of a high consuming test case

Author: nicolas-grekas

src/Symfony/Component/Routing/Tests/Generator/Dumper/PhpGeneratorDumperTest.php

@@ -91,10 +91,10 @@ public function testDumpWithTooManyRoutes()
         }
         $this->routeCollection->add('Test2', new Route('/testing2'));
 
-        $data = $this->generatorDumper->dump(array(
+        file_put_contents($this->largeTestTmpFilepath, $this->generatorDumper->dump(array(
             'class' => 'ProjectLargeUrlGenerator',
-        ));
-        file_put_contents($this->largeTestTmpFilepath, $data);
+        )));
+        $this->routeCollection = $this->generatorDumper = null;
         include $this->largeTestTmpFilepath;
 
         $projectUrlGenerator = new \ProjectLargeUrlGenerator(new RequestContext('/app.php'));