Bump xunit.runner.visualstudio from 2.5.3 to 2.8.1 (#288)

Bumps [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) from 2.5.3 to 2.8.1.
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.3...2.8.1)

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

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

Author: dependabot[bot]

src/Directory.Packages.props

@@ -16,7 +16,7 @@
   <ItemGroup>
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
     <PackageVersion Include="xunit" Version="2.8.0" />
-    <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.3" />
+    <PackageVersion Include="xunit.runner.visualstudio" Version="2.8.1" />
     <PackageVersion Include="FluentAssertions" Version="6.12.0" />
     <PackageVersion Include="Akka.TestKit.Xunit2" Version="$(AkkaVersion)" />
     <PackageVersion Include="NBench" Version="2.0.1" />