build(deps): bump Microsoft.Reactive.Testing from 5.0.0 to 6.0.0 in /…

…src (#1022)

Bumps [Microsoft.Reactive.Testing](https://github.com/dotnet/reactive) from 5.0.0 to 6.0.0.
- [Release notes](https://github.com/dotnet/reactive/releases)
- [Commits](https://github.com/dotnet/reactive/commits)

---
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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/Directory.build.props

@@ -51,7 +51,7 @@
     <PackageReference Include="xunit" Version="2.4.2" />
     <PackageReference Include="Xunit.StaFact" Version="1.1.11" />
     <PackageReference Include="FluentAssertions" Version="6.11.0" />
-    <PackageReference Include="Microsoft.Reactive.Testing" Version="5.0.0" />
+    <PackageReference Include="Microsoft.Reactive.Testing" Version="6.0.0" />
     <PackageReference Include="PublicApiGenerator" Version="11.0.0" />
     <PackageReference Include="Verify.Xunit" Version="20.3.0" />
   </ItemGroup>