Suggest adding event listeners to `events()` in TenancyServiceProvider

[lukinovec]

@stancl, I found only one relevant instance of recommending to put Event::listen(TenancyEvent::class, ...) in the AppServiceProvider (there's also the "prevent Passport migrations from running in the central app" one, but I don't think that's relevant because it's correct to place that in the AppServiceProvider). I made it suggest adding the listener to events() in the TenancyServiceProvider.

[stancl]

Thanks!