Bump xunit.runner.visualstudio from 2.8.0 to 2.8.1 in /src

Bumps [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) from 2.8.0 to 2.8.1.
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.8.0...2.8.1)

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

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

src/Tests/Tests.csproj

@@ -10,7 +10,7 @@
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
     <PackageReference Include="Xunit" Version="2.8.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.10.0" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.0" PrivateAssets="all" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.1" PrivateAssets="all" />
     <ProjectReference Include="..\CountryData.Bogus\CountryData.Bogus.csproj" />
     <ProjectReference Include="..\CountryData\CountryData.csproj" />
     <PackageReference Include="ProjectDefaults" Version="1.0.127" PrivateAssets="all" />