remove unnecessary `util.Dedup` and `util.RightJoinMap` methods #3015

Job	Run time
Build melange and add to artifact cache	43s
Build packages (bubblewrap, hello-wolfi)	1m 23s
Build packages (bubblewrap, glibc)	13m 27s
Build packages (bubblewrap, tini)	1m 11s
Build packages (bubblewrap, lzo)	2m 12s
Build packages (bubblewrap, bubblewrap)	1m 11s
Build packages (bubblewrap, gitsign)	3m 8s
Build packages (bubblewrap, guac)	3m 50s
Build packages (bubblewrap, mdbook)	3m 47s
Build packages (bubblewrap, s3cmd)	1m 9s
Build packages (bubblewrap, perl-yaml-syck)	1m 37s
Build packages (bubblewrap, ncurses)	2m 39s
Build packages (qemu, hello-wolfi)	1m 57s
Build packages (qemu, glibc)	13m 57s
Build packages (qemu, tini)	1m 45s
Build packages (qemu, lzo)	1m 57s
Build packages (qemu, bubblewrap)	2m 11s
Build packages (qemu, gitsign)	3m 23s
Build packages (qemu, guac)	5m 15s
Build packages (qemu, mdbook)	4m 59s
Build packages (qemu, s3cmd)	1m 43s
Build packages (qemu, perl-yaml-syck)	1m 47s
Build packages (qemu, ncurses)	2m 45s
	1h 17m 56s

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