Update Serilog to latest version (2.12.0) in the test project

Author: 0xced

tests/Serilog.Formatting.Log4Net.Tests.csproj

@@ -12,7 +12,7 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.3.2" />
     <PackageReference Include="PublicApiGenerator" Version="10.3.0" />
     <PackageReference Include="ReportGenerator" Version="5.1.10" PrivateAssets="all" />
-    <PackageReference Include="Serilog" Version="2.11.0" />
+    <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="17.10.2" />