header: Move vk.xml to version 1.0.31
header: Move vk.xml to version 1.0.31

Change-Id: If908ba18545c4afc0d041904c0daa57a2569c5a9

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools