databases/qof: Switch to new upstream

The previous upstream has been unfetchable for quite a while.

There are a number of forks, of which https://github.com/GnoTime/qof
seems to be the most active. It is also the same GH account as
is used by deskutils/gnotime, which is our only in-tree consumer.

Take MAINTAINERship and undeprecate.

MFH: 2025Q4
(cherry picked from commit ca25e4212c174b27f1dd0fa9a6d40c29b09813e2)