upgrade System.ServiceModel.Primitives to 4.4.0 because it supports netstandard2.0

Author: valeriob

src/NetMQ/NetMQ.csproj

@@ -69,7 +69,7 @@
   </ItemGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'netstandard2.0' ">
-    <PackageReference Include="System.ServiceModel.Primitives" Version="4.3.0" />
+    <PackageReference Include="System.ServiceModel.Primitives" Version="4.4.0" />
   </ItemGroup>
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'uap10.0' ">