refactor: remove unused parameter in ArtisanServiceProvider

[omarchouman]

This PR removes unused $app parameter from closure that doesn't use the application container instance.

Changes:

• ConfigPublishCommand singleton: Remove unused $app parameter

Benefits:

• Cleaner code that clearly shows when container access is not needed
• Eliminates unused parameter warnings in static analysis tools
• Consistent with Laravel's coding standards

Testing:

• All existing tests continue to pass
• No functional changes to service registration
• Service is still properly registered as singleton

Before:

$this->app->singleton(ConfigPublishCommand::class, function ($app) {
    return new ConfigPublishCommand;
});

After:

$this->app->singleton(ConfigPublishCommand::class, function () {
    return new ConfigPublishCommand;
});