Bump xunit.runner.visualstudio from 2.5.6 to 2.8.1

Bumps [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) from 2.5.6 to 2.8.1.
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.6...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] <support@github.com>

Author: dependabot[bot]

Tests.props

@@ -12,13 +12,13 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.3" Condition="'$(TargetFramework)' == 'netcoreapp2.1'" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" Condition="'$(TargetFramework)' == 'netcoreapp2.1'" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" Condition="'$(TargetFramework)' != 'netcoreapp2.1'" />
     <PackageReference Include="Shouldly" Version="4.2.1" />
     <PackageReference Include="xunit" Version="2.6.6" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" Condition="'$(TargetFramework)' == 'netcoreapp2.1'" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5" Condition="'$(TargetFramework)' == 'netcoreapp3.1' OR '$(TargetFramework)' == 'net5.0'" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.6" Condition="'$(TargetFramework)' != 'netcoreapp2.1' AND '$(TargetFramework)' != 'netcoreapp3.1' AND '$(TargetFramework)' != 'net5.0'" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.1" Condition="'$(TargetFramework)' != 'netcoreapp2.1' AND '$(TargetFramework)' != 'netcoreapp3.1' AND '$(TargetFramework)' != 'net5.0'" />
     <PackageReference Include="Moq" Version="4.20.70" />
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="2.1.*" Condition="'$(TargetFramework)' == 'netcoreapp2.1' OR '$(TargetFramework)' == 'net48'" />
     <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="3.1.*" Condition="'$(TargetFramework)' == 'netcoreapp3.1'" />