Remove obsolete code

modules/notification/api/src/main/scala/docspell/notification/api/PeriodicDueItemsArgs.scala

@@ -12,6 +12,13 @@ import emil.MailAddress
 import io.circe.generic.semiauto
 import io.circe.{Decoder, Encoder}
 
+/** Arguments to the notification task.
+  *
+  * This tasks queries items with a due date and informs the user via mail.
+  *
+  * If the structure changes, there must be some database migration to update or remove
+  * the json data of the corresponding task.
+  */
 final case class PeriodicDueItemsArgs(
     account: AccountId,
     channel: ChannelOrRef,