Bump the xunit group across 1 directory with 2 updates

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


Updates `xunit` from 2.7.0 to 2.8.1
- [Commits](xunit/xunit@2.7.0...2.8.1)

Updates `xunit.runner.visualstudio` from 2.5.7 to 2.8.1
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.7...2.8.1)

---
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] <[email protected]>

test/AssemblyMetadata.Generators.Tests/AssemblyMetadata.Generators.Tests.csproj

@@ -47,8 +47,8 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageReference Include="MinVer" Version="5.0.0" PrivateAssets="All" />
     <PackageReference Include="Verify.Xunit" Version="23.7.1" />
-    <PackageReference Include="xunit" Version="2.7.0" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.7">
+    <PackageReference Include="xunit" Version="2.8.1" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.1">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>