minor #19014 Add implements ProcessorInterface (jschaedl)

This PR was merged into the 6.3 branch.

Discussion
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Add implements ProcessorInterface

The code example is not wrong, but I believe it makes it more understandable if we implement the `ProcessorInterface` to show where the `__invoke` method comes from.
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Commits
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478dbda Add implements ProcessorInterface

Author: OskarStark

logging/processors.rst

@@ -20,10 +20,11 @@ using a processor::
     namespace App\Logger;
 
     use Monolog\LogRecord;
+    use Monolog\Processor\ProcessorInterface;
     use Symfony\Component\HttpFoundation\Exception\SessionNotFoundException;
     use Symfony\Component\HttpFoundation\RequestStack;
 
-    class SessionRequestProcessor
+    class SessionRequestProcessor implements ProcessorInterface
     {
         public function __construct(
             private RequestStack $requestStack