Messenger keeps stacking messages even it is unregistered

### Describe the bug

I have come through this bug and did not find a solution for it, even AI was unable to answer me. So, I think it is a bug in the library.
I have created a sample repo as well as a video showing the behaviour.
The issue in short, is that when you register StrongReferenceMessenger and then unregister it, when you open it again previous messengers registrations will be invoked and stacking messages are in place.

Here is the repo to reproduce

https://github.com/JawadJaber/WpfTestStrongReferenceMessengerStackingIssue

### Regression

_No response_

### Steps to reproduce

https://github.com/user-attachments/assets/d0d69615-8445-46c2-a935-b4985683655a

### Expected behavior

When creating new window twice, the logger should receive only one line message not two.

### Screenshots

_No response_

### IDE and version

VS 2022

### IDE version

_No response_

### Nuget packages

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

### Nuget package version(s)

8.4.0

### Additional context

_No response_

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