remove unnecessary `util.Dedup` and `util.RightJoinMap` methods #3000

Job	Run time
Build melange and add to artifact cache	35s
Build packages (bubblewrap, hello-wolfi)	1m 28s
Build packages (bubblewrap, glibc)	14m 13s
Build packages (bubblewrap, tini)	1m 10s
Build packages (bubblewrap, lzo)	1m 26s
Build packages (bubblewrap, bubblewrap)	1m 11s
Build packages (bubblewrap, gitsign)	3m 18s
Build packages (bubblewrap, guac)	3m 43s
Build packages (bubblewrap, mdbook)	3m 52s
Build packages (bubblewrap, s3cmd)	1m 9s
Build packages (bubblewrap, perl-yaml-syck)	1m 14s
Build packages (bubblewrap, ncurses)	2m 19s
Build packages (qemu, hello-wolfi)	1m 52s
Build packages (qemu, glibc)	14m 6s
Build packages (qemu, tini)	1m 40s
Build packages (qemu, lzo)	1m 53s
Build packages (qemu, bubblewrap)	1m 43s
Build packages (qemu, gitsign)	3m 38s
Build packages (qemu, guac)	4m 42s
Build packages (qemu, mdbook)	4m 30s
Build packages (qemu, s3cmd)	1m 35s
Build packages (qemu, perl-yaml-syck)	1m 45s
Build packages (qemu, ncurses)	2m 37s
	1h 15m 39s

Provide feedback