fix: Fix support of UWP vs. WinUI

[dr1rrb]

linked to https://github.com/unoplatform/uno.csharpmarkup/pull/518

Bugfix

Fix support of UWP vs. WinUI

What is the current behavior?

Build fail

What is the new behavior?

🙃

PR Checklist

Please check if your PR fulfills the following requirements:

• [ ] Tested code with current supported SDKs
• [ ] Docs have been added/updated which fit documentation template. (for bug fixes / features)
• [ ] Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• [ ] Wasm UI Tests are not showing unexpected any differences. Validate PR Screenshots Compare Test Run results.
• [ ] Contains NO breaking changes
• [ ] Updated the Release Notes
• [x] Associated with an issue (GitHub or internal)