Slightly optimize `compliment.sources.namespaces-and-classes/candidates`

[vemv]

Changes (comp distinct concat) -> (into [] (comp cat (distinct)) [,,,]) which should be slightly faster and take less memory.

Cheers - V

[alexander-yakushev]

I've been eyeing this change for some time, but always postponed due to the big diff it generated. But I agree, it's time to finally do it. Thank you:)

[vemv]

Cheers 🍻