Remove "private" from defaults, it already is

symfony/framework-bundle/4.2/config/services.yaml

@@ -10,9 +10,6 @@ services:
     _defaults:
         autowire: true      # Automatically injects dependencies in your services.
         autoconfigure: true # Automatically registers your services as commands, event subscribers, etc.
-        public: false       # Allows optimizing the container by removing unused services; this also means
-                            # fetching services directly from the container via $container->get() won't work.
-                            # The best practice is to be explicit about your dependencies anyway.
 
     # makes classes in src/ available to be used as services
     # this creates a service per class whose id is the fully-qualified class name