chore(deps): bump Verify.Xunit from 28.7.0 to 28.8.1

Bumps [Verify.Xunit](https://github.com/VerifyTests/Verify) from 28.7.0 to 28.8.1.
- [Release notes](https://github.com/VerifyTests/Verify/releases)
- [Commits](https://github.com/VerifyTests/Verify/commits)

---
updated-dependencies:
- dependency-name: Verify.Xunit
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

test/Microsoft.OpenApi.Tests/Microsoft.OpenApi.Tests.csproj

@@ -14,7 +14,7 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
     <PackageReference Include="Moq" Version="4.20.72" />
     <PackageReference Include="SharpYaml" Version="2.1.1" />
-    <PackageReference Include="Verify.Xunit" Version="28.7.0" />
+    <PackageReference Include="Verify.Xunit" Version="28.8.1" />
     <PackageReference Include="xunit" Version="2.9.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.0.0" PrivateAssets="all" />
     <PackageReference Include="Microsoft.CSharp" Version="4.7.0" />