move invalid entry exception

EDPlayerJournal/Entries/Entry.cs

@@ -4,11 +4,6 @@ using System.Runtime.InteropServices;
 
 namespace EDPlayerJournal.Entries;
 
-public class InvalidJournalEntryException : Exception {
-    public InvalidJournalEntryException() { }
-    public InvalidJournalEntryException(string message) : base(message) { }
-}
-
 /// <summary>
 /// Base class for a single entry within the player journal. If no specific sub class is available
 /// this class gives basic information, such as EventType or date when it happened. It also allows