HDR cameras "stack" their tonemapping

## Bevy version

0.15.3

## Relevant system information

```ignore
`AdapterInfo { name: "AMD Radeon RX 7900 XTX (RADV NAVI31)", vendor: 4098, device: 29772, device_type: DiscreteGpu, driver: "radv", driver_info: "Mesa 25.0.3", backend: Vulkan }`
```

## What you did

Copied the [first person view model example](https://bevyengine.org/examples/camera/first-person-view-model/), made both cameras HDR and gave them `Tonemapping::AcesFitted`

## What went wrong

Both not HDR, one `Tonemapping::AcesFitted`, one `Tonemapping::None


Both not HDR, both `Tonemapping::AcesFitted`


Both HDR, one `Tonemapping::AcesFitted`, one `Tonemapping::None


Both HDR, both `Tonemapping::AcesFitted`

As you can see, the two non-HDR screenshots look identical, however the HDR screenshots look different. The difference is a bit subtle, so let me show you how this looks in Foxtrot.

All HDR, one `Tonemapping::AcesFitted`, rest `Tonemapping::None


All HDR, all `Tonemapping::AcesFitted`