minor #20101 doc: add missing use statements (pchabbert)

This PR was squashed before being merged into the 7.1 branch.

Discussion
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doc: add missing use statements

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Commits
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ce13892 doc: add missing use statements

Author: xabbuh

configuration/multiple_kernels.rst

@@ -117,7 +117,9 @@ resources::
     // src/Kernel.php
     namespace Shared;
 
+    use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
     use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
+    use Symfony\Component\HttpKernel\Kernel as BaseKernel;
     use Symfony\Component\Routing\Loader\Configurator\RoutingConfigurator;
 
     class Kernel extends BaseKernel
@@ -258,6 +260,7 @@ the application ID to run under CLI context::
 
     // bin/console
     use Shared\Kernel;
+    use Symfony\Bundle\FrameworkBundle\Console\Application;
     use Symfony\Component\Console\Input\InputInterface;
     use Symfony\Component\Console\Input\InputOption;