Remove general-testing feed

Author: jjonescz

NuGet.config

@@ -22,8 +22,6 @@
     <add key="richnav" value="https://pkgs.dev.azure.com/azure-public/vside/_packaging/vs-buildservices/nuget/v3/index.json" />
     <!-- Used for BenchmarkDotNet prerelease packages -->
     <add key="benchmark-dotnet-prerelease" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/benchmark-dotnet-prerelease/nuget/v3/index.json" />
-    <!-- Used for Roslyn version 4.5.0-2.23107.1 -->
-    <add key="general-testing" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/general-testing/nuget/v3/index.json" />
   </packageSources>
   <!--
     ****************************** AUTOGENERATED ***********************************
@@ -42,10 +40,6 @@
   -->
   <packageSourceMapping>
     <clear />
-    <packageSource key="general-testing">
-      <package pattern="microsoft.*" />
-      <package pattern="microsoft.commonlanguageserverProtocol.*" />
-    </packageSource>
     <packageSource key="dotnet-core-internal-tooling">
       <package pattern="microsoft.*" />
     </packageSource>