Inconsistency in chapter "Rendering Mutliple Objects" with previous chapters and crash on close

While following the chapter on "[Rendering Multiple objects](https://docs.vulkan.org/tutorial/latest/16_Multiple_Objects.html)" I noticed that in the `updateUniformBuffers()` function the up vector in `glm::lookAt` changes from Z to Y. This change isn't explained, so someone who isn't copying the whole snippet and doesn't notice the change could run into problems as in the `setupGameObjects()` function the variables are set assuming this change.

This chapter also doesn't show or tell that the `cleanup()` function was changed leading to a crash when the window is closed.