MarsSeed [1] filed a deletion request for libstdc++-doc [2]: Abandoned, outdated documentation package from 2015. Flagged OOD for 16+ months by me. But this package is not too useful to keep anyway. Most people just browse manuals online, or download directly from upstream website.
[1] https://aur.archlinux.org/account/MarsSeed/ [2] https://aur.archlinux.org/pkgbase/libstdc++-doc/
