Drop no longer needed dependencies

Obsolete after the removal of libKF5{KdePimDBusInterfaces,
FollowupReminder,SendLater}.
1 job for release/20.08 in 20 minutes and 54 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #59413
build_clazy_clang_tidy

00:20:54