Bump FsUnit.xUnit from 5.3.0 to 6.0.0

Bumps [FsUnit.xUnit](https://github.com/fsprojects/FsUnit) from 5.3.0 to 6.0.0.
- [Release notes](https://github.com/fsprojects/FsUnit/releases)
- [Changelog](https://github.com/fsprojects/FsUnit/blob/master/RELEASE_NOTES.md)
- [Commits](fsprojects/FsUnit@5.3.0...6.0.0)

---
updated-dependencies:
- dependency-name: FsUnit.xUnit
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

src/Exercism.TestRunner.FSharp/Exercism.TestRunner.FSharp.fsproj

@@ -23,7 +23,7 @@
     <PackageReference Include="Fantomas.Core" Version="5.1.5" />
     <PackageReference Include="Fantomas.FCS" Version="5.1.5" />
     <PackageReference Include="Humanizer.Core" Version="2.14.1" />
-    <PackageReference Include="FsUnit.xUnit" Version="5.3.0" />
+    <PackageReference Include="FsUnit.xUnit" Version="6.0.0" />
     <PackageReference Update="FSharp.Core" Version="7.0.0" />
   </ItemGroup>