Bump Microsoft.Reactive.Testing from 5.0.0 to 6.0.1

Bumps [Microsoft.Reactive.Testing](https://github.com/dotnet/reactive) from 5.0.0 to 6.0.1.
- [Release notes](https://github.com/dotnet/reactive/releases)
- [Commits](dotnet/reactive@ixnet-v5.0.0...ixnet-v6.0.1)

---
updated-dependencies:
- dependency-name: Microsoft.Reactive.Testing
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

src/Exercism.TestRunner.CSharp/Exercism.TestRunner.CSharp.csproj

@@ -17,7 +17,7 @@
     <PackageReference Include="FakeItEasy" Version="7.4.0" />
     <PackageReference Include="FsCheck" Version="2.16.6" />
     <PackageReference Include="FsCheck.Xunit" Version="2.16.6" />
-    <PackageReference Include="Microsoft.Reactive.Testing" Version="5.0.0" />
+    <PackageReference Include="Microsoft.Reactive.Testing" Version="6.0.1" />
     <PackageReference Include="Sprache" Version="2.3.1" />
   </ItemGroup>