Bump xunit from 2.5.1 to 2.6.6 (#244)

Bumps [xunit](https://github.com/xunit/xunit) from 2.5.1 to 2.6.6.
- [Commits](xunit/xunit@2.5.1...2.6.6)

---
updated-dependencies:
- dependency-name: xunit
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

src/Directory.Packages.props

@@ -23,7 +23,7 @@
     <PackageVersion Include="Akka.Hosting.TestKit" Version="$(AkkaVersion)" />
     <PackageVersion Include="FluentAssertions" Version="6.12.0" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
-    <PackageVersion Include="xunit" Version="2.5.1" />
+    <PackageVersion Include="xunit" Version="2.6.6" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.1" />
     <PackageVersion Include="Akka.TestKit.Xunit2" Version="$(AkkaVersion)" />
     <PackageVersion Include="Akka.Persistence.Sql.TestKit" Version="$(AkkaVersion)" />