Include AccountCacheItemTests

I noticed this was no longer included in the project. Probably should
be.

Author: haacked

src/UnitTests/UnitTests.csproj

@@ -147,6 +147,7 @@
     <Compile Include="GitHub.App\ViewModels\RepositoryCloneViewModelTests.cs" />
     <Compile Include="GitHub.App\ViewModels\RepositoryCreationViewModelTests.cs" />
     <Compile Include="GitHub.App\ViewModels\RepositoryPublishViewModelTests.cs" />
+    <Compile Include="GitHub.Exports.Reactive\Caches\AccountCacheItemTests.cs" />
     <Compile Include="GitHub.Exports\VSServicesTests.cs" />
     <Compile Include="GitHub.Extensions\UriExtensionTests.cs" />
     <Compile Include="GitHub.Primitives\UriStringTests.cs" />
@@ -257,9 +258,7 @@
   <ItemGroup>
     <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
   </ItemGroup>
-  <ItemGroup>
-    <Folder Include="GitHub.Exports.Reactive\" />
-  </ItemGroup>
+  <ItemGroup />
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <Target Name="EnsureNuGetPackageBuildImports" BeforeTargets="PrepareForBuild">
     <PropertyGroup>