Downgrade Serilog requirement to >= 2.0.0

Author: JoshSchreuderMO

src/Serilog.Enrichers.Memory/Serilog.Enrichers.Memory.csproj

@@ -18,7 +18,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Serilog" Version="2.2.0" />
+    <PackageReference Include="Serilog" Version="2.0.0" />
   </ItemGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'net45' ">