Remove async properties from custom.Message
Remove async properties from custom.Message

Awaiting on a property was strange and only really made sense
in events.NewMessage. Methods like client.get_messages() and
similar return entire custom.Message which won't need to touch
the network, and requiring the await was a poor UX.

expectocode/Telethon,LonamiWebs/Telethon,LonamiWebs/Telethon,LonamiWebs/Telethon,LonamiWebs/Telethon