[BUG] Anchor replacement/documentation missing in PopupV2

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Did you read the "Reporting a bug" section on Contributing file?

- [x] I have read the "Reporting a bug" section on Contributing file: https://github.com/CommunityToolkit/Maui/blob/main/CONTRIBUTING.md#reporting-a-bug

### Current Behavior

Anchor was removed in PopupV2, but this is not documented as a breaking change in https://github.com/CommunityToolkit/Maui/wiki/Migrating-to-Popup-v2 and no alternative is provided.

Unfortunately, I have yet to find a workaround for this behavior.

### Expected Behavior

Documentation that it has been removed and what it's suggested replacement is

### Steps To Reproduce

Migrate an app that used Anchor with PopupV2

### Link to public reproduction project repository

N/A

### Environment

```markdown
Unrelated
```

### Anything else?

_No response_