Add proper dependency data for Keysmith: it does not actually need all of KF5
This change deliberately does not include the liboath/oath-toolkit dependency (which wasn't listed previously either): this just fixes the KF5 dependencies.

Update git repo of kde-build-metadata, run kdesrc-build --no-metadata --dependency-tree keysmith and verify the listed dependencies.
Check the top-level CMakeLists.txt file of Keysmith for find_package() stanzas.