minor #17398 [DependencyInjection] Show how to get $myService (tacman)

This PR was submitted for the 6.1 branch but it was squashed and merged into the 4.4 branch instead.

Discussion
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[DependencyInjection] Show how to get $myService

Fixes #17397, makes it clearer how to get the service, since ->get() isn't correct and getDefinition() isn't obvious.

Commits
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95b8fea [DependencyInjection] Show how to get $myService

Author: javiereguiluz

service_container/service_subscribers_locators.rst

@@ -467,6 +467,8 @@ will share identical locators among all the services referencing them::
             // ...
             'logger' => new Reference('logger'),
         ];
+        
+        $myService = $container->findDefinition(MyService::class);
 
         $myService->addArgument(ServiceLocatorTagPass::register($container, $locateableServices));
     }