Removing Xamarin.iOS10 from nuspec

Hopefully this would enforce Xamarin to work with netstandard2.0.

Author: darkl

NuGet/WampSharp.nuspec

@@ -46,12 +46,6 @@
         <dependency id="System.Reactive" version="[3.0.0, 3.1.1]" />
         <dependency id="System.ValueTuple" version="[4.4.0, )" />
       </group>
-      <group targetFramework="Xamarin.iOS10">
-        <dependency id="System.Reactive" version="[3.0.0, 3.1.1]" />
-        <dependency id="System.Collections.Immutable" version="[1.3.1, )" />
-        <dependency id="System.Threading.Tasks.Dataflow" version="[4.7.0, )" />
-        <dependency id="System.ValueTuple" version="[4.4.0, )" />
-      </group>
     </dependencies>
     <id>WampSharp</id>
     <title>WampSharp</title>