TokenizingTextBox will Delete More Tokens Than Expected when Some Tokens Have Same Content

### Describe the bug

Tokens with same content will be deleted when other tokens with same contents deleted by using backspace key. **Plus, only the tokens in TokenizingSample have this problem.**

### Steps to reproduce

```text
1. Create tokens like Pic 1 below.
2. select a token having same content with at least one token.(In the picture, we select "Account")
3. Press backspace, all tokens with same content will be deleted.
P.S.: if the token is not in TokenizingSample, the bug won't be reproduced, Pic 2 below is an Example.
```

### Expected behavior

Only selected token will be deleted.

### Screenshots


Pic 1


Pic 2

### Code Platform

- [X] UWP
- [ ] WinAppSDK / WinUI 3
- [ ] Web Assembly (WASM)
- [ ] Android
- [ ] iOS
- [ ] MacOS
- [ ] Linux / GTK

### Windows Build Number

- [ ] Windows 10 1809 (Build 17763)
- [ ] Windows 10 1903 (Build 18362)
- [ ] Windows 10 1909 (Build 18363)
- [ ] Windows 10 2004 (Build 19041)
- [ ] Windows 10 20H2 (Build 19042)
- [ ] Windows 10 21H1 (Build 19043)
- [ ] Windows 10 21H2 (Build 19044)
- [ ] Windows 10 22H2 (Build 19045)
- [ ] Windows 11 21H2 (Build 22000)
- [X] Other (specify)

### Other Windows Build number

Windows 11 23H2 (Build 22635.3139)

### App minimum and target SDK version

- [ ] Windows 10, version 1809 (Build 17763)
- [ ] Windows 10, version 1903 (Build 18362)
- [ ] Windows 10, version 1909 (Build 18363)
- [ ] Windows 10, version 2004 (Build 19041)
- [ ] Windows 10, version 2104 (Build 20348)
- [ ] Windows 11, version 22H2 (Build 22000)
- [ ] Other (specify)

### Other SDK version

_No response_

### Visual Studio Version

_No response_

### Visual Studio Build Number

_No response_

### Device form factor

_No response_

### Additional context

_No response_

### Help us help you

No, I'm unable to contribute a solution.

まず TokenizingTextBox コントロールと TokenizingSample から始め、重複した内容のトークンを作成して、そのうちの 1 つで Backspace を押すことで問題を再現します。TokenizingSample で選択したトークンだけが削除され、同じ内容のトークンが残れば完了です。

索引モデルが issue の本文から書いたものです。