Add comment to samples using `SimulatedLocationDataSource`

Because a `SimulatedLocationDataSource` is created from a file or local data, it doesn't require requesting permission for device location. When a developer copy code from such a sample, they may miss the step to call `CLLocationManager().requestWhenInUseAuthorization()`.

Add a comment in those samples to explain that when swapping out simulated LDS for system LDS, one need to request permission.