mms auto_config bitmessage json has binary
mms auto_config is failing because the JSON sent via bitmessage JSON can't deserialize 

```
$ ./monero-wallet-cli --version
Monero 'Fluorine Fermi' (v0.18.2.2-release)
```

```
2023-09-28 22:56:17.590     7f8c8ffb76c0        ERROR   default contrib/epee/include/storages/portable_storage_from_json.h:88   Wrong JSON character at: BM-2cT3rK2mqxVNbWAmk5MdU2Wz28TsvoYggC
2023-09-28 22:56:17.590     7f8c8ffb76c0        ERROR   default contrib/epee/include/storages/portable_storage_from_json.h:403  Failed to parse json, what: Wrong JSON character at: BM-2cT3rK2mqxVNbWAmk5MdU2Wz28TsvoYggC
2023-09-28 22:56:17.590     7f8c8ffb76c0        ERROR   wallet.mms      src/wallet/message_transporter.cpp:124  Failed to deserialize messages
```

from testnet wallets:

```
{
  "content": "g,'8*$BR\"mIUW_vqF#e:ߧ_ ofe?H\bcdKTikD`V@su",
  "destination_monero_address": {
    "m_spend_public_key": "��������������������������������",
    "m_view_public_key": "��������������������������������"
  },
  "destination_transport_address": "BM-2cSrgeeXv5oEvBLMzTaX7zmvVGJV1XanWz",
  "encryption_public_key": "fK\/6dG=>�*\v)g)2",
  "hash": "q).U\"HSUv&lQ",
  "iv": "9eMi",
  "round": 0,
  "signature": ")ez'8=&LITx\tt\vc\t8\v}ܹ+򇅚.Yoz\n",
  "signature_count": 0,
  "source_monero_address": {
    "m_spend_public_key": "\v#pݕLZSzҙ!BI",
    "m_view_public_key": "r-o@�7EfKaU,+{>"
  },
  "source_transport_address": "BM-2cXibCmyMyGBsCt1RN5DBsiUkWWpr1FtnV",
  "subject": "MMS V0 2023-09-28 22:31:59",
  "timestamp": 1695940319,
  "transport_id": "",
  "type": 7
}
```