There's a merged pull request on the void-packages repository

libunique{,1}: remove package
https://github.com/void-linux/void-packages/pull/38873

Description:
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#### Testing the changes
- I tested the changes in this PR: **briefly**

Long deprecated, only really dependended on by gnome applications that have been unmaintained since 2012/2011.
https://gitlab.gnome.org/Archive/unique

Its functionality was superseded by glib and gtk+3:
https://web.archive.org/web/20110307044005/http://library.gnome.org/devel/gtk3/stable/gtk-migrating-GtkApplication.html

gmpc is a gtk2 client for mpd, of which there are [plenty of alternatives](https://www.musicpd.org/clients/). It is unmaintained as of 2011.
libmpd has been replaced by libmpdclient and isn't depended on by anything.
gnac is a gtk2 audio conversion utility of which there are better alternatives for. It is unmaintained as of 2012.

Prerequisites for libunique1:
- [x] https://github.com/void-linux/void-packages/pull/38866
- [x] https://github.com/void-linux/void-packages/pull/38867
- [x] https://github.com/void-linux/void-packages/pull/38868
- [x] https://github.com/void-linux/void-packages/pull/38869

Prerequisites for libunique:
- [x] https://github.com/void-linux/void-packages/pull/38870
- [x] https://github.com/void-linux/void-packages/pull/38871
- [x] https://github.com/void-linux/void-packages/pull/38872

Closes: https://github.com/void-linux/void-packages/pull/38848

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