demos:Add const to fix build warning
demos:Add const to fix build warning

Explicit "const" for ppEnabledExtensionNames to fix build warning.

fixup

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