minor #15392 Fixing code sample (ThomasLandauer)

This PR was merged into the 4.4 branch.

Discussion
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Fixing code sample

This is now the usual way to do it, right? https://symfony.com/doc/current/configuration.html#configuration-parameters

In any case, `->setParameter()` results in:
> Call to undefined method "Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator::setParameter()".

Commits
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f16dac0 Fixing code sample

Author: javiereguiluz

performance.rst

@@ -80,7 +80,7 @@ container into a single file, which could improve performance when using
         // config/services.php
 
         // ...
-        $container->setParameter('container.dumper.inline_factories', true);
+        $container->parameters()->set('container.dumper.inline_factories', true);
 
 .. _performance-use-opcache: