A problem when Korean letter is typed into a TextBox control loaded inside a PopUp control

### Description

When I type a Korean letter inside the TextBox control, which is loaded inside the PopUp control, the first typed letter is not updated in the TextBox. When I type the second letter, both the first and the second letters are updated. This behavior continues with further typing.

## Please find the code snippet below: ##
```

```

## Please find the sample to replicate the issue: ##
[KoreanIEM_SimpleSample.zip](https://github.com/user-attachments/files/16110130/KoreanIEM_SimpleSample.zip)

## Please find the video reference below: ##

https://github.com/dotnet/wpf/assets/104507189/2e1561a1-b455-49cb-abcc-35df7a59643a

### Reproduction Steps

1. Run the sample.
2. Click the "Click to Open Popup" button.
3. Type a Korean letter inside the Textbox
4. Then type another Korean letter.

### Expected behavior

The Korean letter should be able to update simultaneously when typing.

### Actual behavior

The Korean letter shouldn't to update simultaneously when typing.

### Regression?

_No response_

### Known Workarounds

_No response_

### Impact

_No response_

### Configuration

.NET version -> .NET framework 4.8.1
OS version -> Windows 11 Enterprise & Version - 22H2

### Other information

_No response_