Fix a few examples of the SS API

They all had a `room_id` field, which doesn't match the definition.

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

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

@@ -76,7 +76,6 @@ paths:
                             $ref: ../../event-schemas/examples/invite_room_state.json
               type: object
             example: {
-              "room_id": "!somewhere:example.org",
               "type": "m.room.member",
               "state_key": "@joe:elsewhere.com",
               "origin": "example.org",

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

@@ -81,7 +81,6 @@ paths:
             example: {
               "room_version": "2",
               "event": {
-                "room_id": "!somewhere:example.org",
                 "type": "m.room.member",
                 "state_key": "@joe:elsewhere.com",
                 "origin": "example.org",

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

@@ -140,7 +140,6 @@ paths:
                 - type
                 - content
             example: {
-              "room_id": "!somewhere:example.org",
               "type": "m.room.member",
               "state_key": "@someone:example.org",
               "origin": "example.org",

data/api/server-server/knocks.yaml

@@ -270,7 +270,6 @@ paths:
                 - type
                 - content
             example: {
-              "room_id": "!somewhere:example.org",
               "type": "m.room.member",
               "state_key": "@someone:example.org",
               "origin": "example.org",