try to fix appveyor failing to build sample lib.fsproj

Author: smoothdeveloper

src/SqlClient.TestProjects/Lib/Lib.fsproj

@@ -18,7 +18,8 @@
     <Content Include="App.config" />
   </ItemGroup>
   <ItemGroup>
-    <Reference Include="netstandard" />
+    <!-- TODO: investigate why netstandard assembly was put here, or if it is the thing breaking appveyor for #430 -->
+    <!--<Reference Include="netstandard" />-->
     <Reference Condition="'$(TargetFramework)' == 'netstandard2.0'" Include="FSharp.Data.SqlClient">
       <HintPath>..\..\..\bin\netstandard2.0\FSharp.Data.SqlClient.dll</HintPath>
     </Reference>