Remove the origin field on PUT /send_join responses

This is a spec bug as it has actually never been sent by Synapse, going back to 2014.

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

data/api/server-server/joins-v1.yaml

@@ -339,9 +339,6 @@ paths:
                       title: Room State
                       description: The state for the room.
                       properties:
-                        origin:
-                          type: string
-                          description: The resident server's [server name](/appendices/#server-name).
                         auth_chain:
                           type: array
                           description: |-
@@ -371,13 +368,11 @@ paths:
                       required:
                         - auth_chain
                         - state
-                        - origin
               examples:
                 response:
                   value: [
                     200,
                     {
-                      "origin": "matrix.org",
                       "auth_chain": [
                         {
                           "$ref": "examples/minimal_pdu.json"

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

@@ -160,9 +160,6 @@ paths:
               schema:
                 type: object
                 properties:
-                  origin:
-                    type: string
-                    description: The resident server's [server name](/appendices/#server-name).
                   members_omitted:
                     type: boolean
                     description: "`true` if `m.room.member` events have been omitted from `state`."
@@ -222,11 +219,9 @@ paths:
                 required:
                   - auth_chain
                   - state
-                  - origin
               examples:
                 response:
                   value: {
-                    "origin": "matrix.org",
                     "auth_chain": [
                       {
                         "$ref": "examples/minimal_pdu.json"