Revert "fix api diff."

This reverts commit 7470b94cdf.

# Conflicts:
#	build/ApiDiff.props

build/ApiDiff.props

@@ -4,9 +4,9 @@
     <NugetPackageName Condition="'$(PackageId)' != ''">$(PackageId)</NugetPackageName>
     <NugetPackageName Condition="'$(PackageId)' == ''">Avalonia</NugetPackageName>
   </PropertyGroup>
-    <!--<ItemGroup>
+    <ItemGroup>
       <PackageDownload Include="$(NugetPackageName)" Version="[$(ApiContractPackageVersion)]" />
       <PackageReference Include="Microsoft.DotNet.ApiCompat" Version="5.0.0-beta.20372.2" PrivateAssets="All" />
       <ResolvedMatchingContract Include="$(NuGetPackageRoot)\$(NugetPackageName.ToLowerInvariant())\$(ApiContractPackageVersion)\lib\$(TargetFramework)\$(AssemblyName).dll" />
-    </ItemGroup>-->
+    </ItemGroup>
 </Project>