Remove dependency on netstandard.library

Author: wtgodbe

Directory.Build.targets

@@ -132,10 +132,6 @@
       <TargetingPackVersion Condition="'$(IsServicingBuild)' != 'true'">$(SharedFxVersion)</TargetingPackVersion>
     </KnownFrameworkReference>
 
-    <KnownFrameworkReference Update="NETStandard.Library">
-      <TargetingPackVersion Condition="'%(TargetFramework)' == 'netstandard2.1' and '$(IsServicingBuild)' != 'true'">$(NETStandardLibraryRefPackageVersion)</TargetingPackVersion>
-    </KnownFrameworkReference>
-
     <!-- Track compiler separately from Arcade.-->
     <PackageReference Include="Microsoft.Net.Compilers.Toolset"
         Version="$(MicrosoftNetCompilersToolsetPackageVersion)"

eng/Version.Details.xml

@@ -385,10 +385,6 @@
       <Uri>https://github.com/dotnet/core-setup</Uri>
       <Sha>4a9f85e9f89d7f686fef2ae2109d876b1e2eed2a</Sha>
     </Dependency>
-    <Dependency Name="NETStandard.Library.Ref" Version="2.1.0" Pinned="true">
-      <Uri>https://github.com/dotnet/core-setup</Uri>
-      <Sha>7d57652f33493fa022125b7f63aad0d70c52d810</Sha>
-    </Dependency>
     <Dependency Name="Microsoft.NETCore.App.Internal" Version="3.1.3-servicing.20128.1" CoherentParentDependency="Microsoft.Extensions.Logging">
       <Uri>https://github.com/dotnet/core-setup</Uri>
       <Sha>4a9f85e9f89d7f686fef2ae2109d876b1e2eed2a</Sha>

eng/Versions.props

@@ -70,7 +70,6 @@
     <MicrosoftNETCoreAppInternalPackageVersion>3.1.3-servicing.20128.1</MicrosoftNETCoreAppInternalPackageVersion>
     <MicrosoftNETCoreAppRefPackageVersion>3.1.0</MicrosoftNETCoreAppRefPackageVersion>
     <MicrosoftNETCoreAppRuntimewinx64PackageVersion>3.1.3</MicrosoftNETCoreAppRuntimewinx64PackageVersion>
-    <NETStandardLibraryRefPackageVersion>2.1.0</NETStandardLibraryRefPackageVersion>
     <!-- Packages from dotnet/corefx -->
     <MicrosoftBclAsyncInterfacesPackageVersion>1.1.0</MicrosoftBclAsyncInterfacesPackageVersion>
     <MicrosoftCSharpPackageVersion>4.7.0</MicrosoftCSharpPackageVersion>