docs: Remove references to "this repo"
docs: Remove references to "this repo"

Remove references to "this repository" in the loader and layers design doc since this file can appear on web sites, etc.
KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers