minor #4445 Removed unnecessary use statement (Alex Salguero)

This PR was merged into the 2.3 branch.

Discussion
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Removed unnecessary use statement

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets |

Found a rather unnecessary "use" statement in the code example in the "debugging" cookbook. Makes it difficult to spot the changes between one code example and the following one and know what changed.

Commits
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6a9162b Removed unnecessary use statement in code example in the debugging cookbook

cookbook/debugging.rst

@@ -47,8 +47,6 @@ below::
     $loader = require_once __DIR__.'/../app/autoload.php';
     require_once __DIR__.'/../app/AppKernel.php';
 
-    use Symfony\Component\HttpFoundation\Request;
-
     $kernel = new AppKernel('dev', true);
     // $kernel->loadClassCache();
     $request = Request::createFromGlobals();