Responses schema fixes (#3650)
Fixes #2237.
Corrects the response schemas for:
```
PUT /user/{user_id}/account_data/{account_dataType}
PUT /user/{user_id}/rooms/{roomId}/account_data/{type}
PUT /directory/list/room/{roomId}
PUT /sendToDevice/{eventType}/{txnId}
POST /account/3pid
POST /account/3pid/add
POST /account/3pid/bind
```
