Update WinUI Dependency

[dotMorten]

Description

Windows App SDK v1.6 is now required

Type of change

• Other enhancement

Platforms tested on

• WPF .NET 8
• WPF Framework
• WinUI
• MAUI WinUI
• MAUI Android
• MAUI iOS
• MAUI MacCatalyst

Checklist

• Self-review of changes
• All changes work as expected on all affected platforms
• There are no warnings related to changes
• Code is commented and follows .NET conventions and standards
• Codemaid and XAML styler extensions have been run on every changed file
• No unrelated changes have been made to any other code or project files
• Screenshots are correct size and display in description tab (800 x 600 on Windows, MAUI mobile platforms use the MAUI Windows screenshot)