Cleaned up CommunityToolkit.Authentication.Uwp csproj file

[shweaver-MSFT]

Fixes #

PR Type

What kind of change does this PR introduce?

• Bugfix

What is the current behavior?

It was reported that there are issues building the CommunityToolkit.Authentication.Uwp project, so I took the opportunity to clean up the csproj file and make it more similar to that of UWP projects in WCT.

PR Checklist

Please check if your PR fulfills the following requirements:

• [x] Tested code with current supported SDKs
• [x] Sample in sample app has been added / updated (for bug fixes / features)
  • [ ] Icon has been created (if new sample) following the Thumbnail Style Guide and templates
• [ ] Tests for the changes have been added (for bug fixes / features) (if applicable)
• [x] Header has been added to all new source files (run build/UpdateHeaders.bat)
• [x] Contains NO breaking changes

Other information

[ghost]

Thanks shweaver-MSFT for opening a Pull Request! The reviewers will test the PR and highlight if there is any merge conflict or changes required. If the PR is approved we will proceed to merge the pull request 🙌