build(deps): Bump xunit.runner.visualstudio from 2.5.5 to 2.5.6 (#287)

Bumps [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) from 2.5.5 to 2.5.6.
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.5...2.5.6)

---
updated-dependencies:
- dependency-name: xunit.runner.visualstudio
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

src/ReactiveMarbles.PropertyChanged.Tests/ReactiveMarbles.PropertyChanged.Tests.csproj

@@ -17,7 +17,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
     <PackageReference Include="xunit" Version="2.6.4" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.5" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.6" />
     <PackageReference Include="Xunit.StaFact" Version="1.1.11" />
     <PackageReference Include="PublicApiGenerator" Version="11.1.0" />
   </ItemGroup>