nip10: simplify and fix reply-to-root bugs

This removes EventRefs alltogether and uses the form we use in Damus
Android.

This simplifies our ThreadReply logic and fixes a reply-to-root bug

Reported-by: NotBiebs <justinbieber@stemstr.app>
Changelog-Fixed: Fix thread bug where a quote isn't picked up as a reply
Signed-off-by: William Casarin <jb55@jb55.com>

damus/Models/ContentFilters.swift

@@ -16,7 +16,7 @@ enum FilterState : Int {
     func filter(ev: NostrEvent) -> Bool {
         switch self {
         case .posts:
-            return ev.known_kind == .boost || !ev.is_reply(.empty)
+            return ev.known_kind == .boost || !ev.is_reply()
         case .posts_and_replies:
             return true
         }