[Sample App] Add <UseMaui>true</UseMaui>

[ne0rrmatrix]

• Bug fix

Description of Change

Revert removal of <UseMaui>true<</UseMaui> in sample csproj

Linked Issues

• Fixes [BUG] Community toolkit project cannot build sample project #2056

PR Checklist

• Has a linked Issue, and the Issue has been approved(bug) or Championed (feature/proposal)
• Has tests (if omitted, state reason in description)
• Has samples (if omitted, state reason in description)
• Rebased on top of main at time of PR
• Changes adhere to coding standard
• Documentation created or updated: https://github.com/MicrosoftDocs/CommunityToolkit/pulls

Additional information

Fixes cannot build and/or run on any device/emulator.

[VladislavAntonyuk]

Should it only be reverted for Sample project or all projects?

[filipnavara]

Should it only be reverted for Sample project or all projects?

Libraries should not need it. UseMaui is somewhat misleadingly deprecated since .NET 8 with a warning (the warning message is incorrect though: dotnet/maui#20658).

[GeorgeLeithead]

Should it only be reverted for Sample project or all projects?

Libraries should not need it. UseMaui is somewhat misleadingly deprecated since .NET 8 with a warning (the warning message is incorrect though: dotnet/maui#20658).

I gave it all a try from a fresh clone (with a restore and workload restore). Without the UseMaui in the libraries, it all works perfectly fine as long as the "actual" MAUI project (in this case "Sample") has the UseMaui, as indicated by @filipnavara.

I also ran all of the Unit Tests, and they pass with 100%.