Fix builds on MacOS

[jsuarezruiz]

The current error is:

025-07-09T08:35:53.6237760Z /Users/runner/.dotnet/packs/Microsoft.MacCatalyst.Sdk.net10.0_18.4/18.4.10622-net10-p5/targets/Xamarin.Shared.Sdk.targets(2172,3): error : This version of Microsoft.MacCatalyst requires the MacCatalyst 18.4.10622-net10-p5 SDK (shipped with Xcode 16.3). The current version of Xcode is 16.4. Either install Xcode 16.3, or use a different version of Microsoft.MacCatalyst. See https://aka.ms/xcode-requirement for more information. [/Users/runner/work/maui-samples/maui-samples/10.0/Fundamentals/ClassHierarchy/ClassHierarchy/ClassHierarchy.csproj::TargetFramework=net10.0-maccatalyst]
2025-07-09T08:35:53.6244610Z /Users/runner/.dotnet/packs/Microsoft.iOS.Sdk.net10.0_18.4/18.4.10622-net10-p5/targets/Xamarin.Shared.Sdk.targets(2172,3): error : This version of Microsoft.iOS requires the iOS 18.4.10622-net10-p5 SDK (shipped with Xcode 16.3). The current version of Xcode is 16.4. Either install Xcode 16.3, or use a different version of Microsoft.iOS. See https://aka.ms/xcode-requirement for more information.

This PR updates the CI workflow to use the latest .NET 10 preview SDK and runtime to resolve build errors caused by an Xcode version mismatch.