graphics/digikam: unbreak build after KDE PIM 23.04 (+)

In KDE PIM 23.04 the KF5:: targets have been renamed to KPim5::
While the KF5:: targets are kept for backwards compatibility, they no longer recursively include other KF5:: targets.
We need to search for Akonadi explicitly so that the KF5::AkonadiCore target is defined.

Backport from: https://invent.kde.org/graphics/digikam/-/commit/5b4ba173f6a84a8be1131b1523dc42df95171ec7