Remove dependency on System.Net.Primitives (#403)

This is a relic from the pre v1.0.0 days, where the IP Address type was (incorrectly) used to force a strong type onto Gateway.

Signed-off-by: timyhac <timyhac@gmail.com>

Author: timyhac

src/libplctag.NativeImport/libplctag.NativeImport.csproj

@@ -33,8 +33,4 @@
     <None Include="..\..\docs\libplctag.NativeImport.md" Pack="true" PackagePath="\README.md"/>
   </ItemGroup>
 
-  <ItemGroup>
-    <PackageReference Include="System.Net.Primitives" Version="4.3.1" />
-  </ItemGroup>
-
 </Project>