RenderLayers does not affect SceneBundle

## Bevy version

Latest bevy git commit at time of writing, `8f721d8d0ac2e14a46051175f6d3394ed87c7214`.

## Relevant system information

```ignore
`AdapterInfo { name: "NVIDIA GeForce RTX 2070", vendor: 4318, device: 7938, device_type: DiscreteGpu, backend: Vulkan }`
```

## What you did

I noticed this issue in my current project. I also tried adding the component `RenderLayers::layer(1)` to the SceneBundle in the split_screen example.

## What went wrong

The component has no effect.