Update to Serilog 3.1 RTM

Author: nblumhardt

src/Serilog.Formatting.Compact/Serilog.Formatting.Compact.csproj

@@ -28,7 +28,7 @@
     </PropertyGroup>
 
     <ItemGroup>
-        <PackageReference Include="Serilog" Version="3.1.0-*" />
+        <PackageReference Include="Serilog" Version="3.1.0" />
         <None Include="../../assets/serilog-extension-nuget.png" Pack="True" Visible="False" PackagePath="" />
         <None Include="../../README.md" Pack="True" Visible="False" PackagePath="" />
     </ItemGroup>