update to latest xunit

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

@@ -34,8 +34,8 @@
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   <ItemGroup>
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-    <PackageReference Include="xunit" Version="2.2.0-beta4-build3465" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.2.0-beta4-build1205" />
+    <PackageReference Include="xunit" Version="2.2.0-beta4-build3466" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.2.0-beta4-build1209" />
     <ProjectReference Include="..\System.Reactive\System.Reactive.csproj" />
     <ProjectReference Include="..\System.Reactive.Observable.Aliases\System.Reactive.Observable.Aliases.csproj" />
     <ProjectReference Include="..\Microsoft.Reactive.Testing\Microsoft.Reactive.Testing.csproj" />