layers: Removing redundant if in unique_objects
layers: Removing redundant if in unique_objects

Exact same if check performed multiple times.
Removing redundant one

Change-Id: Iff32a724e58a06b4a967ba2632e60cc5b4050238

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