Update Microsoft.Extensions.Configuration to v6.0.

This upgrade was enabled by removing the net45 target in a929097.

Author: bgrainger

tests/IntegrationTests/IntegrationTests.csproj

@@ -32,9 +32,9 @@
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5" />
     <!--app packages-->
     <PackageReference Include="Dapper.StrongName" Version="2.0.123" />
-    <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="1.1.2" />
-    <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="1.1.2" />
-    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="1.1.2" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="6.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="6.0.1" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="6.0.0" />
     <Using Include="System" />
     <Using Include="System.Data" />
     <Using Include="System.Data.Common" />
@@ -57,6 +57,7 @@
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'net462' OR '$(TargetFramework)' == 'net472' ">
     <Reference Include="System" />
+    <Reference Include="System.Net.Http" />
     <Reference Include="System.Transactions" />
     <Reference Include="Microsoft.CSharp" />
   </ItemGroup>