Fix references in nuspec

- Resolves nanoframework/Home#711.

Author: josesimoes

nanoFramework.WebServer.nuspec

@@ -27,9 +27,9 @@
       <dependency id="nanoFramework.Runtime.Events" version="1.9.0-preview.14" />
       <dependency id="nanoFramework.System.Collections" version="1.2.0-preview.29" />
       <dependency id="nanoFramework.System.Text" version="1.1.1-preview.29" />
-      <dependency id="nanoFramework.System.Net" version="1.3.3-preview.50" />
+      <dependency id="nanoFramework.System.Net" version="1.6.3-preview.33" />
       <dependency id="nanoFramework.System.Net.Http.Server" version="1.3.3-preview.55" />
-      <dependency id="nanoFramework.Windows.Storage" version="1.10.1-preview.24" />
+      <dependency id="nanoFramework.Windows.Storage" version="1.4.4-preview.45" />
       <dependency id="nanoFramework.Windows.Storage.Streams" version="1.10.1-preview.24" />
     </dependencies>
   </metadata>