Readd PublicSign project property

Author: dsteinweg

src/Serilog.Enrichers.Environment/Serilog.Enrichers.Environment.csproj

@@ -6,6 +6,7 @@
         <AssemblyVersion>3.0.0.0</AssemblyVersion>
         <SignAssembly>true</SignAssembly>
         <AssemblyOriginatorKeyFile>../../assets/Serilog.snk</AssemblyOriginatorKeyFile>
+        <PublicSign Condition=" '$(OS)' != 'Windows_NT' ">true</PublicSign>
         <Authors>Serilog Contributors</Authors>
         <!-- .NET Framework version targeting is frozen at these two TFMs. -->
         <TargetFrameworks Condition=" '$(OS)' == 'Windows_NT'">net471;net462</TargetFrameworks>