[vulkan linux] Fix native_platform_handle with gtk

Use gtk connection as handle and use it when creating surface.

src/xenia/ui/vulkan/vulkan_context.cc

@@ -73,10 +73,6 @@ bool VulkanContext::Initialize() {
 #ifdef GDK_WINDOWING_X11
     GtkWidget* window_handle =
         static_cast<GtkWidget*>(target_window_->native_handle());
-    GdkDisplay* gdk_display = gtk_widget_get_display(window_handle);
-    assert(GDK_IS_X11_DISPLAY(gdk_display));
-    xcb_connection_t* connection =
-        XGetXCBConnection(gdk_x11_display_get_xdisplay(gdk_display));
     xcb_window_t window =
         gdk_x11_window_get_xid(gtk_widget_get_window(window_handle));
     VkXcbSurfaceCreateInfoKHR create_info;