[BUG] [ObservableProperty] OnChanged Callback Not Firing with TwoWay Binding

### Describe the bug

When using [ObservableProperty] from CommunityToolkit.Mvvm 8.4 on a bool property bound TwoWay to Microsoft.Maui.Controls.Picker.IsOpen, the generated OnIsProjectPickerExpandedChanged method is never called

### Regression

8.0.3

### Steps to reproduce

- Run the ObservablePropertyIssue sample attached in this https://github.com/SuthiYuvaraj/Samples/tree/main/ObservablePropertyIssue repository.
- Open the Picker and select an item.
- After selecting the item, the SelectionText is not updated. The PropertyChanged notification is never raised.

```csharp

public partial class MainPageViewModel : ObservableObject
{
[ObservableProperty]
private bool _isProjectPickerExpanded;

[ObservableProperty]
private string _selectionText = "No project selected";

partial void OnIsProjectPickerExpandedChanged(bool value)
{
SelectionText = value
? "Picker is open..."
: SelectedProject is not null
? $"Selected: {SelectedProject.Name} – {SelectedProject.Description}"
: "No project selected";
}

// ...
}
```
With reference to the code snippet , OnIsProjectPickerExpandedChanged is never called.

### Expected behavior

The OnIsProjectPickerExpandedChanged PropertyChanged method is expected to be invoked whenever the IsOpen property changes.

### Screenshots

_No response_

### IDE and version

VS 2022

### IDE version

_No response_

### Nuget packages

- [ ] CommunityToolkit.Common
- [ ] CommunityToolkit.Diagnostics
- [ ] CommunityToolkit.HighPerformance
- [ ] CommunityToolkit.Mvvm (aka MVVM Toolkit)

### Nuget package version(s)

8.0.4

### Additional context

- .NET MAUI CommunityToolkit:8.0.4
- OS: MacCatalyst Xcode 26.2
- .NET MAUI:11.0.0-preview.1.26104.11

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