Rewrite RemoteMembers' docstring
Rewrite RemoteMembers' docstring

* Specify that it is a list of expected recipients, and that all members
  are also members of the call.
* Mention mute.
* Compare and contrast with LocalSendingState
* Mention that all senders will also be represented in
  RemoteMediaDescriptions in the streamed media case.

TelepathyIM/telepathy-spec,freedesktop-unofficial-mirror/telepathy__telepathy-spec