fix: UAP referencing wrong version in events

Author: glennawatson

src/ReactiveUI.Events/ReactiveUI.Events.csproj

@@ -16,10 +16,10 @@
   </ItemGroup>
 
   <ItemGroup Condition="  $(TargetFramework.StartsWith('uap')) ">
-    <SDKReference Include="WindowsDesktop, Version=10.0.17763.0">
+    <SDKReference Include="WindowsDesktop, Version=10.0.16299.0">
       <Name>Windows Desktop Extensions for the UWP</Name>
     </SDKReference>
-    <SDKReference Include="WindowsMobile, Version=10.0.17763.0"> 
+    <SDKReference Include="WindowsMobile, Version=10.0.16299.0"> 
       <Name>Windows Mobile Extensions for the UWP</Name> 
     </SDKReference> 
     <Compile Include="Events_uwp.cs" Condition="Exists('Events_uwp.cs')" />