Fix docs for scheduled event's cover (#1667)

fix docs for scheduled event's cover

Co-authored-by: BobDotCom <[email protected]>

Author: honzajavorek

discord/scheduled_events.py

@@ -312,7 +312,7 @@ async def edit(
             so there is no need to change this parameter.
         reason: Optional[:class:`str`]
             The reason to show in the audit log.
-        cover: Optional[:class:`Asset`]
+        cover: Optional[:class:`bytes`]
             The cover image of the scheduled event.
 
         Returns