remove json.net from ios core project

src/iOS.Core/iOS.Core.csproj

@@ -34,9 +34,6 @@
     <ConsolePause>false</ConsolePause>
   </PropertyGroup>
   <ItemGroup>
-    <Reference Include="Newtonsoft.Json, Version=12.0.0.0, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed, processorArchitecture=MSIL">
-      <HintPath>..\..\packages\Newtonsoft.Json.12.0.2\lib\netstandard2.0\Newtonsoft.Json.dll</HintPath>
-    </Reference>
     <Reference Include="System" />
     <Reference Include="System.Xml" />
     <Reference Include="System.Core" />
@@ -62,8 +59,5 @@
       <Name>Core</Name>
     </ProjectReference>
   </ItemGroup>
-  <ItemGroup>
-    <None Include="packages.config" />
-  </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath)\Xamarin\iOS\Xamarin.iOS.CSharp.targets" />
 </Project>

src/iOS.Core/packages.config

@@ -1,4 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<packages>
-  <package id="Newtonsoft.Json" version="12.0.2" targetFramework="xamarinios10" />
-</packages>