Bump Verify.Xunit from 28.11.0 to 28.12.1

Bumps [Verify.Xunit](https://github.com/VerifyTests/Verify) from 28.11.0 to 28.12.1.
- [Release notes](https://github.com/VerifyTests/Verify/releases)
- [Commits](VerifyTests/Verify@28.11.0...28.12.1)

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

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

Author: dependabot[bot]

tests/Serilog.Formatting.Log4Net.Tests.csproj

@@ -15,7 +15,7 @@
     <PackageReference Include="Serilog" Version="4.2.0" />
     <PackageReference Include="Serilog.Enrichers.Environment" Version="3.0.1" />
     <PackageReference Include="Serilog.Enrichers.Thread" Version="4.0.0" />
-    <PackageReference Include="Verify.Xunit" Version="28.11.0" />
+    <PackageReference Include="Verify.Xunit" Version="28.12.1" />
     <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.0.2" PrivateAssets="all" />
   </ItemGroup>