Bump the xunit group with 2 updates (#200)

Bumps the xunit group with 2 updates: [xunit](https://github.com/xunit/xunit) and [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit).


Updates `xunit` from 2.7.1 to 2.8.0
- [Commits](xunit/xunit@2.7.1...2.8.0)

Updates `xunit.runner.visualstudio` from 2.5.8 to 2.8.0
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.8...2.8.0)

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

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

test/Serilog.Sinks.Splunk.TCP.Tests/Serilog.Sinks.Splunk.TCP.Tests.csproj

@@ -11,8 +11,8 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
-    <PackageReference Include="xunit" Version="2.7.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.8">
+    <PackageReference Include="xunit" Version="2.8.0" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.0">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>

test/Serilog.Sinks.Splunk.Tests/Serilog.Sinks.Splunk.Tests.csproj

@@ -10,8 +10,8 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
-    <PackageReference Include="xunit" Version="2.7.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.8">
+    <PackageReference Include="xunit" Version="2.8.0" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.0">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>