layers: Fix memory leak in instance destroy_dispatch_table
layers: Fix memory leak in instance destroy_dispatch_table

Change-Id: I8152960f30f73a997386aa9bf3561d2e0e8b408d

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