layers: Remove unused string helper from CV
layers: Remove unused string helper from CV

Change-Id: I36daf405a6c8170d7ee61f5a07bdad045f8d6304

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