Confusing snippets concerns settings of physical devices

[NanFeiDeXuMu]

This is the web: https://docs.vulkan.org/tutorial/latest/03_Drawing_a_triangle/00_Setup/03_Physical_devices_and_queue_families.html

The declaration and assignment of physicalDevice seems inconsistent and the compiler reported an error.
Plus it cannot be initialized by default due to the raii properties.

Compiled on wins x86-64, Visual Studio 2022 with the latest version of Vulkan. Thanks for your kindly support.

[SaschaWillems]

This was fixed in #173