Fix Ribbon control PackageId evaluation order

Move Import statement before PackageId PropertyGroup to ensure
$(PackageIdVariant) is defined when PackageId is evaluated.

Previously, PackageId referenced $(PackageIdVariant) before the
Import that defines it, resulting in malformed package identifiers
like 'CommunityToolkit..Controls.Ribbon' (with empty variable).

This prevented Ribbon packages from being published to NuGet feeds.

All other controls have Import before PackageId and work correctly.
This aligns Ribbon with the established pattern.

Fixes #739

Author: Arlodotexe

components/Ribbon/src/CommunityToolkit.WinUI.Controls.Ribbon.csproj

@@ -10,12 +10,13 @@
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
 
+  <!-- Sets this up as a toolkit component's source project -->
+  <Import Project="$(ToolingDirectory)\ToolkitComponent.SourceProject.props" />
+
   <PropertyGroup>
     <PackageId>$(PackageIdPrefix).$(PackageIdVariant).Controls.$(ToolkitComponentName)</PackageId>
   </PropertyGroup>
 
-  <!-- Sets this up as a toolkit component's source project -->
-  <Import Project="$(ToolingDirectory)\ToolkitComponent.SourceProject.props" />
   <ItemGroup>
     <UpToDateCheckInput Remove="RibbonStyle.xaml" />
   </ItemGroup>