gnome-user-docs: update to 3.28.0.
gnome-user-docs: update to 3.28.0.

[ci skip]

Closes: #12531 [via git-merge-pr]

coredumb/void-packages,coredumb/void-packages,NeoChontrix/void-packages,NeoChontrix/void-packages,necrophcodr/void-packages,coredumb/void-packages,NeoChontrix/void-packages,NeoChontrix/void-packages,NeoChontrix/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,NeoChontrix/void-packages,necrophcodr/void-packages,necrophcodr/void-packages,coredumb/void-packages,coredumb/void-packages,coredumb/void-packages