Bump Verify.Xunit from 20.3.2 to 21.2.0

Bumps [Verify.Xunit](https://github.com/VerifyTests/Verify) from 20.3.2 to 21.2.0.
- [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-major
...

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

Author: dependabot[bot]

tests/Serilog.Formatting.Log4Net.Tests.csproj

@@ -16,7 +16,7 @@
     <PackageReference Include="Serilog" Version="2.12.0" />
     <PackageReference Include="Serilog.Enrichers.Environment" Version="2.2.0" />
     <PackageReference Include="Serilog.Enrichers.Thread" Version="3.1.0" />
-    <PackageReference Include="Verify.Xunit" Version="20.3.2" />
+    <PackageReference Include="Verify.Xunit" Version="21.2.0" />
     <PackageReference Include="xunit" Version="2.5.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5" PrivateAssets="all" />
   </ItemGroup>