remove workaround

Directory.Build.targets

@@ -51,30 +51,4 @@
       RemoveProperties="TargetFramework"
       StopOnFirstFailure="True" />
   </Target>
-
-  <!-- BEGIN workaround for https://github.com/dotnet/sdk/issues/43339; remove after updated to VS 17.12, future 17.11 patch or when arcade ships the the same workaround -->
-  <Target Name="WorkaroundDotnetSdk43339" BeforeTargets="ResolvePackageAssets" Condition=" '$(MSBuildRuntimeType)' == 'Full' and $([MSBuild]::VersionLessThan($(MSBuildVersion), 17.12.0))">
-    <PrimeSystemTextJson804 />
-  </Target>
-  <UsingTask
-    TaskName="PrimeSystemTextJson804"
-    TaskFactory="RoslynCodeTaskFactory"
-    AssemblyFile="$(MSBuildToolsPath)\Microsoft.Build.Tasks.Core.dll" >
-    <Task>
-      <Code Type="Fragment" Language="cs">
-<![CDATA[
-try
-{
-    System.Reflection.Assembly.LoadFrom(@"$(MicrosoftNETBuildTasksDirectoryRoot)\..\..\..\DotnetTools\dotnet-format\BuildHost-net472\System.Text.Json.dll");
-}
-catch
-{
-    // Best effort: if something moves in the SDK don't break the build.
-}
-]]>
-      </Code>
-    </Task>
-  </UsingTask>
-  <!-- END workaround for https://github.com/dotnet/sdk/issues/43339 -->
-
 </Project>