vkconfig3: $VULKAN_SDK on macOS

[richard-lunarg]

Under the system diagnostic tab on macOS, near the top is this line:

• ${VULKAN_SDK}: /usr/local/share/vulkan

This is confusing to me, as $VULKAN_SDK (actually all environment variables) are not set for GUI applications. When it is set via
source setup-env.sh it is actually something like:
/Users/lunarg/VulkanSDK/1.3.302.0/macOS

This could be clearer for macOS users what this is representing.