build: Remove Mock ICD JSON file from install target
build: Remove Mock ICD JSON file from install target

The mock ICD shouldn't be installed or be part of packages
that use the "make install" target to create packages.
The mock ICD shared lib wasn't added, but the JSON was.

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