Bump xunit.runner.visualstudio from 2.5.8 to 2.8.1

Bumps [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) from 2.5.8 to 2.8.1.
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.8...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]

SickRfid.Tests/SickRfid.Tests.csproj

@@ -16,7 +16,7 @@
     <ItemGroup>
       <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.10.0" />
       <PackageReference Include="xunit" Version="2.7.1" />
-      <PackageReference Include="xunit.runner.visualstudio" Version="2.5.8">
+      <PackageReference Include="xunit.runner.visualstudio" Version="2.8.1">
         <PrivateAssets>all</PrivateAssets>
         <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       </PackageReference>