remove redundant .author field from filter spec.

fixes https://github.com/fiatjaf/nostr/issues/34.

nips/01.md

@@ -62,7 +62,6 @@ Clients can send 3 types of messages, which must be JSON arrays, according to th
 ```
 {
   "id": <the id of an event>,
-  "author": <the pubkey of an event that identifies its author>,
   "kind": <a kind number>
   "#e": <an event id that is referenced in an "e" tag>,
   "#p": <a pubkey that is referenced in a "p" tag>,