header: Move vk.xml to version 1.0.25
header: Move vk.xml to version 1.0.25

Change-Id: I7f24c5a5cbfa00e3f8bc331b63fb26c8912da2dd

KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers,KhronosGroup/Vulkan-LoaderAndValidationLayers