minor #18550 [Console] Minor tweaks (alexandre-daubois)

This PR was merged into the 5.4 branch.

Discussion
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[Console] Minor tweaks

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Commits
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4851edd [Console] Minor tweaks

Author: javiereguiluz

console/calling_commands.rst

@@ -27,7 +27,7 @@ method)::
     {
         // ...
 
-        protected function execute(InputInterface $input, OutputInterface $output): void
+        protected function execute(InputInterface $input, OutputInterface $output): int
         {
             $command = $this->getApplication()->find('demo:greet');
 

console/verbosity.rst

@@ -69,7 +69,7 @@ level. For example::
                 OutputInterface::VERBOSITY_VERBOSE
             );
 
-            return 0;
+            return Command::SUCCESS;
         }
     }