message: Fixed mistake in GSG
diff: @@ -275,13 +275,13 @@ After the connection is established **Faber** must create new DID record that he
  6. **Steward** asks the ledger for the Verification key of **Faber's** DID by calling ``did.key_for_did``.
  ```python
  # Steward Agent
  - faber_verkey = await did.key_for_did(pool_handle, from_wallet, faber_did_info['did'])
  + faber_steward_verkey = await did.key_for_did(pool_handle, from_wallet, faber_steward_did)
  ```
  7. **Steward** authenticates **Faber** by comparison of the Message Sender Verkey and the **Faber** Verkey received from the Ledger.
  ```python
  # Steward Agent
  - assert sender_verkey == faber_verkey
  + assert sender_verkey == faber_steward_verkey
  ```
  8. **Steward** sends the corresponded NYM transaction to the Ledger with `TRUST ANCHOR` role.
  