Update to latest serilog

Author: nojaf

Serilog.Sinks.Network/Serilog.Sinks.Network.csproj

@@ -11,6 +11,6 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Serilog" Version="2.9.0"/>
+    <PackageReference Include="Serilog" Version="4.2.0"/>
   </ItemGroup>
 </Project>