Downgrade to match latest in VS2019

Author: GrahamTheCoder

CommandLine/CodeConv/CodeConv.csproj

@@ -28,7 +28,7 @@ For a nugetted dll, web converter or visual studio extension, see https://github
   </ItemGroup>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="6.0.0" />
+    <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="5.0.0" />
     <PackageReference Include="Microsoft.Build.Locator" Version="1.4.1" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp.Workspaces" Version="4.1.0" />
     <PackageReference Include="Microsoft.CodeAnalysis.VisualBasic.Workspaces" Version="4.1.0" />