Remove reference to facades\System.Reactive in test projects

Rx.NET/Source/tests/Tests.System.Reactive.ApiApprovals/Tests.System.Reactive.ApiApprovals.csproj

@@ -19,7 +19,6 @@
   </ItemGroup>
 
   <ItemGroup>
-    <ProjectReference Include="..\..\facades\System.Reactive\System.Reactive.csproj" />
     <ProjectReference Include="..\..\src\System.Reactive\System.Reactive.csproj" />
     <ProjectReference Include="..\..\src\System.Reactive.Observable.Aliases\System.Reactive.Observable.Aliases.csproj" />
     <ProjectReference Include="..\..\src\Microsoft.Reactive.Testing\Microsoft.Reactive.Testing.csproj" />

Rx.NET/Source/tests/Tests.System.Reactive/Tests.System.Reactive.csproj

@@ -32,7 +32,6 @@
     <PackageReference Include="MSTest.TestAdapter" Version="3.6.1" />
     <PackageReference Include="MSTest.TestFramework" Version="3.6.1" />
     <PackageReference Include="xunit.assert" Version="2.8.0" />
-    <ProjectReference Include="..\..\facades\System.Reactive\System.Reactive.csproj" />
     <ProjectReference Include="..\..\src\System.Reactive\System.Reactive.csproj" />
     <ProjectReference Include="..\..\src\System.Reactive.Observable.Aliases\System.Reactive.Observable.Aliases.csproj" />
     <ProjectReference Include="..\..\src\Microsoft.Reactive.Testing\Microsoft.Reactive.Testing.csproj" />