Bump Verify.Xunit from 17.10.2 to 18.0.0

Bumps [Verify.Xunit](https://github.com/VerifyTests/Verify) from 17.10.2 to 18.0.0.
- [Release notes](https://github.com/VerifyTests/Verify/releases)
- [Commits](VerifyTests/Verify@17.10.2...18.0.0)

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

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

Author: dependabot[bot]

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

@@ -20,7 +20,7 @@
     <PackageReference Include="Moq" Version="4.18.2" />
     <PackageReference Include="Newtonsoft.Json" Version="13.0.1" />
     <PackageReference Include="SharpYaml" Version="2.1.0" />
-    <PackageReference Include="Verify.Xunit" Version="17.10.2" />
+    <PackageReference Include="Verify.Xunit" Version="18.0.0" />
     <PackageReference Include="xunit" Version="2.4.2" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
       <PrivateAssets>all</PrivateAssets>