Guide: remove outdated ScopedWaiter from Device

Author: karnkaul

guide/src/initialization/device.md

@@ -57,38 +57,3 @@ Declare a `vk::Queue` member (order doesn't matter since it's just a handle, the
 	static constexpr std::uint32_t queue_index_v{0};
 	m_queue = m_device->getQueue(m_gpu.queue_family, queue_index_v);
 ```
-
-## ScopedWaiter
-
-A useful abstraction to have is an object that in its destructor waits/blocks until the Device is idle. Being able to do arbitary things on scope exit is useful in general too, but it requires some custom class template like `UniqueResource<Type, Deleter>`. We shall "abuse" `std::unique_ptr<Type, Deleter>` instead: it will not manage the pointer (`Type*`) at all, but instead `Deleter` will call a member function on it (if it isn't null).
-
-Adding this to a new header `scoped_waiter.hpp`:
-
-```cpp
-class ScopedWaiter {
-  public:
-	ScopedWaiter() = default;
-
-	explicit ScopedWaiter(vk::Device const* device) : m_device(device) {}
-
-  private:
-	struct Deleter {
-		void operator()(vk::Device const* device) const noexcept {
-			if (device == nullptr) { return; }
-			device->waitIdle();
-		}
-	};
-	std::unique_ptr<vk::Device const, Deleter> m_device{};
-};
-```
-
-This requires the passed `vk::Device*` to outlive itself, so to be defensive we make `App` be non-moveable and non-copiable, and create a member factory function for waiters:
-
-```cpp
-	auto operator=(App&&) = delete;
-// ...
-
-	[[nodiscard]] auto create_waiter() const -> ScopedWaiter {
-		return ScopedWaiter{&*m_device};
-	}
-```