Remove unnecessary xaml includes.

vsix/ItemTemplates/ViewModel/ViewModel.cpp

@@ -4,9 +4,6 @@
 #include "$safeitemname$.g.cpp"
 #endif
 
-using namespace winrt;
-using namespace Windows::UI::Xaml;
-
 namespace winrt::$rootnamespace$::implementation
 {
     int32_t $safeitemname$::MyProperty()

vsix/ProjectTemplates/VC/Windows Universal/WindowsRuntimeComponent/pch.h

@@ -2,10 +2,3 @@
 #include <unknwn.h>
 #include <winrt/Windows.Foundation.h>
 #include <winrt/Windows.Foundation.Collections.h>
-#include <winrt/Windows.UI.Xaml.h>
-#include <winrt/Windows.UI.Xaml.Controls.h>
-#include <winrt/Windows.UI.Xaml.Controls.Primitives.h>
-#include <winrt/Windows.UI.Xaml.Data.h>
-#include <winrt/Windows.UI.Xaml.Interop.h>
-#include <winrt/Windows.UI.Xaml.Markup.h>
-#include <winrt/Windows.UI.Xaml.Navigation.h>