Remove old conferencing doc

This old document from 2015 has no connection to the current state of
conferencing, so best to remove it to avoid confusion.

docs/conferencing.md

@@ -1,52 +0,0 @@
-# VoIP Conferencing
-
-This is a draft proposal for a naive voice/video conferencing implementation for
-Matrix clients.  There are many possible conferencing architectures possible for
-Matrix (Multipoint Conferencing Unit (MCU); Stream Forwarding Unit (SFU); Peer-
-to-Peer mesh (P2P), etc; events shared in the group room; events shared 1:1;
-possibly even out-of-band signalling).
-
-This is a starting point for a naive MCU implementation which could provide one
-possible Matrix-wide solution in  future, which retains backwards compatibility
-with standard 1:1 calling.
-
- * A client chooses to initiate a conference for a given room by starting a
-   voice or video call with a 'conference focus' user.  This is a virtual user
-   (typically Application Service) which implements a conferencing bridge.  It
-   isn't defined how the client discovers or selects this user.
-
- * The conference focus user MUST join the room in which the client has
-   initiated the conference - this may require the client to invite the
-   conference focus user to the room, depending on the room's `join_rules`. The
-   conference focus user needs to be in the room to let the bridge eject users
-   from the conference who have left the room in which it was initiated, and aid
-   discovery of the conference by other users in the room.  The bridge
-   identifies the room to join based on the user ID by which it was invited.
-   The format of this identifier is implementation dependent for now.
-
- * If a client leaves the group chat room, they MUST be ejected from the
-   conference. If a client leaves the 1:1 room with the conference focus user,
-   they SHOULD be ejected from the conference.
-
- * For now, rooms can contain multiple conference focus users - it's left to
-   user or client implementation to select which to converge on.  In future this
-   could be mediated using a state event (e.g. `im.vector.call.mcu`), but we
-   can't do that right now as by default normal users can't set arbitrary state
-   events on a room.
-
- * To participate in the conference, other clients initiates a standard 1:1
-   voice or video call to the conference focus user.
-
- * For best UX, clients SHOULD show the ongoing voice/video call in the UI
-   context of the group room rather than 1:1 with the focus user.  If a client
-   recognises a conference user present in the room, it MAY chose to highlight
-   this in the UI (e.g. with a "conference ongoing" notification, to aid
-   discovery).  Clients MAY hide the 1:1 room with the focus user (although in
-   future this room could be used for floor control or other direct
-   communication with the conference focus)
-
- * When all users have left the conference, the 'conference focus' user SHOULD
-   leave the room.
-
- * If a conference focus user joins a room but does not receive a 1:1 voice or
-   video call, it SHOULD time out after a period of time and leave the room.