chore(deps): update rx.net (system.reactive) to 6.1.0 (#4162)

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<hr>

This PR contains the following updates:

| Package | Change | Age | Confidence |
|---|---|---|---|
|
[Microsoft.Reactive.Testing](https://redirect.github.com/dotnet/reactive)
| `6.0.2` -> `6.1.0` |
[![age](https://developer.mend.io/api/mc/badges/age/nuget/Microsoft.Reactive.Testing/6.1.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/nuget/Microsoft.Reactive.Testing/6.0.2/6.1.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
| [System.Reactive](https://redirect.github.com/dotnet/reactive) |
`6.0.2` -> `6.1.0` |
[![age](https://developer.mend.io/api/mc/badges/age/nuget/System.Reactive/6.1.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/nuget/System.Reactive/6.0.2/6.1.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

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src/Directory.Packages.props

@@ -24,8 +24,8 @@
     <PackageVersion Include="NUnit" Version="4.4.0" />
     <PackageVersion Include="NUnit3TestAdapter" Version="5.1.0" />
     <PackageVersion Include="NUnit.Analyzers" Version="4.10.0" />
-    <PackageVersion Include="Microsoft.Reactive.Testing" Version="6.0.2" />
-    <PackageVersion Include="System.Reactive" Version="6.0.2" />
+    <PackageVersion Include="Microsoft.Reactive.Testing" Version="6.1.0" />
+    <PackageVersion Include="System.Reactive" Version="6.1.0" />
     <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="8.0.0" />
     <PackageVersion Include="Microsoft.Windows.SDK.BuildTools" Version="10.0.26100.6584" />
     <PackageVersion Include="Microsoft.Xaml.Behaviors.Wpf" Version="1.1.135" />