message: Disable UI overlay for triangle sample
  Fixes validation layer errors
  Refs
diff: @@ -114,6 +114,8 @@ public:
  VulkanExample() : VulkanExampleBase(ENABLE_VALIDATION)
  {
  title = "Vulkan Example - Basic indexed triangle";
  + // To keep things simple, we don't use the UI overlay
  + settings.overlay = false;
  // Setup a default look-at camera
  camera.type = Camera::CameraType::lookat;
  camera.setPosition(glm::vec3(0.0f, 0.0f, -2.5f));
  