Class Library $DotNetVersion$ fix (#4408)

adding back the $DotNetVersion$ customparam that is needed to resolve the TargetFramework
---------

Co-authored-by: Shashank Nayak <shasnayak@microsoft.com>

dev/VSIX/ProjectTemplates/Desktop/CSharp/ClassLibrary/ProjectTemplate.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>$DotNetVersion$-windows10.0.19041.0</TargetFramework>
     <TargetPlatformMinVersion>10.0.17763.0</TargetPlatformMinVersion>
@@ -7,9 +7,5 @@
     <RuntimeIdentifiers Condition="$([MSBuild]::GetTargetFrameworkVersion('$(TargetFramework)')) &lt; 8">win10-x86;win10-x64;win10-arm64</RuntimeIdentifiers>
     <UseWinUI>true</UseWinUI>
   </PropertyGroup>
-
-  <ItemGroup>
-      <PackageReference Include="Microsoft.WindowsAppSDK" Version="$WindowsAppSDKNupkgVersion$" />
-      <PackageReference Include="Microsoft.Windows.SDK.BuildTools" Version="$WindowsSDKBuildToolsNupkgVersion$" />
-  </ItemGroup>
+  
 </Project>

dev/VSIX/ProjectTemplates/Desktop/CSharp/ClassLibrary/WinUI.Desktop.Cs.ClassLibrary.vstemplate

@@ -29,6 +29,7 @@
     </Project>
     <CustomParameters>
       <CustomParameter Name="$NuGetPackages$" Value="Microsoft.WindowsAppSDK;Microsoft.Windows.SDK.BuildTools"/>
+      <CustomParameter Name="$DotNetVersion$" Value="FIXME-Verify-Directory.Build.Targets-XmlPoke-Queries"/>        
     </CustomParameters>
   </TemplateContent>
   <WizardExtension>