winrt: Fix capabilities query.

Windows Runtime port supports non-fullscreen and multiple windows.

Change-Id: I6f4791a7c329ece88e5f6f9910f3635a7bfef3f8
Reviewed-by: Andrew Knight <andrew.knight@intopalo.com>

src/plugins/platforms/winrt/qwinrtintegration.cpp

@@ -188,9 +188,9 @@ bool QWinRTIntegration::hasCapability(QPlatformIntegration::Capability cap) cons
     case ThreadedPixmaps:
     case OpenGL:
     case ApplicationState:
-        return true;
     case NonFullScreenWindows:
-        return false;
+    case MultipleWindows:
+        return true;
     default:
         return QPlatformIntegration::hasCapability(cap);
     }