minor #19191 Update console.rst (hbgamra)

This PR was submitted for the 6.3 branch but it was merged into the 5.4 branch instead.

Discussion
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Update console.rst

remove $kernel variable

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Commits
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625e432 Update console.rst

Author: OskarStark

console.rst

@@ -513,8 +513,8 @@ console::
     {
         public function testExecute()
         {
-            $kernel = self::bootKernel();
-            $application = new Application($kernel);
+            self::bootKernel();
+            $application = new Application(self::$kernel);
 
             $command = $application->find('app:create-user');
             $commandTester = new CommandTester($command);