fix benchmarking project

(cherry picked from commit 002a73a)

Author: Mpdreamz

src/Tests/Tests.Benchmarking/Tests.Benchmarking.csproj

@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <Import Project="$([MSBuild]::GetDirectoryNameOfFileAbove($(MSBuildThisFileDirectory), build.bat))\src\Artifacts.build.props" />
   <PropertyGroup>
-    <TargetFrameworks Condition="'$(OS)' == 'Windows_NT'">netstandard2.0;net461</TargetFrameworks>
-    <TargetFrameworks Condition="'$(OS)' != 'Windows_NT'">netstandard2.0</TargetFrameworks>
+    <TargetFrameworks Condition="'$(OS)' == 'Windows_NT'">netcoreapp2.1;net461</TargetFrameworks>
+    <TargetFrameworks Condition="'$(OS)' != 'Windows_NT'">netcoreapp2.1</TargetFrameworks>
     <OutputType>Exe</OutputType>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)' == 'Debug' ">