uwp: Update WebTiledLayer service

[mstefarov]

Description

Updates the service used for UWP's LoadWebTiledLayer sample to match the service used on other platforms. Old service is no longer online.

Also updates screenshot and metadata.

Type of change

• Bug fix

Platforms tested on

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

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)

[duffh]

Nice!