Fix computed.target_info not being updated after RenderTarget::None is modified (#23593)

# Objective

- Keep `camera.computed.target_info` properly synced with
`RenderTarget::None` changes.
- Fixes #23437

## Solution

- Now `NormalizedRenderTargetExt::is_changed` returns `true` for
`NormalizedRenderTarget::None` instead of `false` (not sure if this was
the best solution, but I don't know any better to figure this out alone)

## Testing

- Created a new testbed (not included in the PR since I've just used for
local testing) using the code described in the issue and compared the
output

---

## Showcase

Now `camera.computed.target_info` is synced with `RenderTarget::None`
changes:

```
2026-03-31T00:40:17.175057Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(512, 512), scale_factor: 1.0 }), None { size: UVec2(512, 512) }
2026-03-31T00:40:17.283301Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(200, 200), scale_factor: 1.0 }), None { size: UVec2(200, 200) }
2026-03-31T00:40:17.869969Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(211, 211), scale_factor: 1.0 }), None { size: UVec2(211, 211) }
2026-03-31T00:40:17.905642Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(233, 233), scale_factor: 1.0 }), None { size: UVec2(233, 233) }
2026-03-31T00:40:17.912143Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(256, 256), scale_factor: 1.0 }), None { size: UVec2(256, 256) }
2026-03-31T00:40:17.925634Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(257, 257), scale_factor: 1.0 }), None { size: UVec2(257, 257) }
2026-03-31T00:40:17.943608Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(259, 259), scale_factor: 1.0 }), None { size: UVec2(259, 259) }
2026-03-31T00:40:17.959604Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(260, 260), scale_factor: 1.0 }), None { size: UVec2(260, 260) }
2026-03-31T00:40:17.973438Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(262, 262), scale_factor: 1.0 }), None { size: UVec2(262, 262) }
2026-03-31T00:40:17.990005Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(263, 263), scale_factor: 1.0 }), None { size: UVec2(263, 263) }
2026-03-31T00:40:18.004798Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(264, 264), scale_factor: 1.0 }), None { size: UVec2(264, 264) }
2026-03-31T00:40:18.016958Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(265, 265), scale_factor: 1.0 }), None { size: UVec2(265, 265) }
2026-03-31T00:40:18.029493Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(266, 266), scale_factor: 1.0 }), None { size: UVec2(266, 266) }
2026-03-31T00:40:18.042025Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(267, 267), scale_factor: 1.0 }), None { size: UVec2(267, 267) }
2026-03-31T00:40:18.054427Z  INFO testbed_bug: Some(RenderTargetInfo { physical_size: UVec2(268, 268), scale_factor: 1.0 }), None { size: UVec2(268, 268) }
```

Co-authored-by: Carter Anderson <mcanders1@gmail.com>

Author: kaio-matos

crates/bevy_render/src/camera.rs

@@ -321,8 +321,7 @@ impl NormalizedRenderTargetExt for NormalizedRenderTarget {
             NormalizedRenderTarget::Image(image_target) => {
                 changed_image_handles.contains(&image_target.handle.id())
             }
-            NormalizedRenderTarget::TextureView(_) => true,
-            NormalizedRenderTarget::None { .. } => false,
+            NormalizedRenderTarget::TextureView(_) | NormalizedRenderTarget::None { .. } => true,
         }
     }
 }