Removed System.Windows.Forms dependency in WPF nuspec file

Author: Jonathan Taylor

Build/NuGet/HtmlRenderer.WPF.nuspec

@@ -35,7 +35,6 @@
     <releaseNotes>See http://htmlrenderer.codeplex.com/releases.</releaseNotes>
     <tags>html render renderer draw control WPF</tags>
     <frameworkAssemblies>
-      <frameworkAssembly assemblyName="System.Windows.Forms" targetFramework="" />
       <frameworkAssembly assemblyName="System.Drawing" targetFramework="" />
     </frameworkAssemblies>
     <dependencies>