Revert "Update to .NET Core 2.1"

This reverts commit 0ab257f6cd.

WebViewer/Microsoft.BPerf.StackViewer/Microsoft.BPerf.StackViewer.csproj

@@ -1,14 +1,14 @@
 <Project Sdk="Microsoft.NET.Sdk.Web">
 
   <PropertyGroup>
-    <TargetFramework>netcoreapp2.1</TargetFramework>
+    <TargetFramework>netcoreapp2.0</TargetFramework>
     <CodeAnalysisRuleSet>StyleCop.Analyzers.ruleset</CodeAnalysisRuleSet>
     <MvcRazorCompileOnPublish>true</MvcRazorCompileOnPublish>
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.1.4" />
+    <PackageReference Include="Microsoft.AspNetCore.All" Version="2.0.6" />
-    <PackageReference Include="Newtonsoft.Json" Version="11.0.2" />
+    <PackageReference Include="Newtonsoft.Json" Version="11.0.1" />
     <PackageReference Include="StyleCop.Analyzers" Version="1.0.2" />
     <PackageReference Include="Microsoft.BPerf.Dia2Lib" Version="1.0.0" />
   </ItemGroup>