minor #16118 Correction for testing commands (epitre)

This PR was submitted for the 5.4 branch but it was merged into the 4.4 branch instead.

Discussion
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Correction for testing commands

The kernel has to be booted and not created

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Commits
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25dae6c Correction for testing commands

Author: javiereguiluz

console.rst

@@ -361,7 +361,7 @@ console::
     {
         public function testExecute()
         {
-            $kernel = static::createKernel();
+            $kernel = self::bootKernel();
             $application = new Application($kernel);
 
             $command = $application->find('app:create-user');