Remove invite_room_state, knock_room_state from the CS API. Fix examples in SS API

changelogs/client_server/newsfragments/1273.clarification

@@ -0,0 +1 @@
+Remove references to `unsigned.{invite_room_state,knock_room_state}` in `m.room.member` events. Clients should use [`invite_state`](https://spec.matrix.org/v1.4/client-server-api/#_matrixclientv3sync_invitestate) to retrieve stripped state events from rooms they've been invited to or knocked on.

changelogs/server_server/newsfragments/1273.clarification

@@ -0,0 +1 @@
+Remove superfluous `unsigned.invite_room_state` dictionary in the [`PUT /_matrix/federation/v2/invite/{roomId}/{eventId}`](https://spec.matrix.org/v1.4/server-server-api/#put_matrixfederationv2inviteroomideventid) response example.

data/api/server-server/invites-v2.yaml

@@ -128,11 +128,6 @@ paths:
                 "origin": "example.org",
                 "origin_server_ts": 1549041175876,
                 "sender": "@someone:example.org",
-                "unsigned": {
-                  "invite_room_state": {
-                    "$ref": "../../event-schemas/examples/invite_room_state.json"
-                  }
-                },
                 "content": {
                     "membership": "invite"
                 },

data/event-schemas/schema/m.room.member.yaml

@@ -18,10 +18,6 @@ description: |-
 
   The `third_party_invite` property will be set if this invite is an `invite` event and is the successor of an `m.room.third_party_invite` event, and absent otherwise.
 
-  This event may also include an `invite_room_state` key inside the event's `unsigned` data.
-  If present, this contains an array of [stripped state events](/client-server-api/#stripped-state)
-  to assist the receiver in identifying the room.
-
   The user for which a membership applies is represented by the `state_key`. Under some conditions,
   the `sender` and `state_key` may not match - this may be interpreted as the `sender` affecting
   the membership state of the `state_key` user.
@@ -136,28 +132,5 @@ properties:
     allOf:
       - $ref: "core-event-schema/unsigned_prop.yaml"
       - type: object
-        properties:
-          invite_room_state:
-            description: |-
-              A subset of the state of the room at the time of the invite, if `membership` is `invite`.
-              Note that this state is informational, and SHOULD NOT be trusted; once the client has
-              joined the room, it SHOULD fetch the live state from the server and discard the
-              invite_room_state. Also, clients must not rely on any particular state being present here;
-              they SHOULD behave properly (with possibly a degraded but not a broken experience) in
-              the absence of any particular events here. If they are set on the room, at least the
-              state for `m.room.avatar`, `m.room.canonical_alias`, `m.room.join_rules`, and `m.room.name`
-              SHOULD be included.
-            items:
-              $ref: "core-event-schema/stripped_state.yaml"
-            type: array
-          knock_room_state:
-            description: |-
-              A subset of the state of the room at the time of the knock, if `membership` is `knock`.
-              This has the same restrictions as `invite_room_state`. If they are set on the room, at least
-              the state for `m.room.avatar`, `m.room.canonical_alias`, `m.room.join_rules`, `m.room.name`,
-              and `m.room.encryption` SHOULD be included.
-            items:
-              $ref: "core-event-schema/stripped_state.yaml"
-            type: array
 title: The current membership state of a user in the room.
 type: object