message: updated old code under Common Errors in readme
diff: @@ -140,10 +140,10 @@ Error `WalletAlreadyExistsError`.
  Delete wallet before creating:
  ```python
  try:
  - await wallet.create_wallet(pool_name, wallet_name, None, None, wallet_credentials)
  + await wallet.create_wallet(wallet_config, wallet_credentials)
  except IndyError:
  await wallet.delete_wallet(wallet_name, wallet_credentials)
  - await wallet.create_wallet(pool_name, wallet_name, None, None, wallet_credentials)
  + await wallet.create_wallet(wallet_config, wallet_credentials)
  ```
  Error `CommonIOError`. Make sure that you have set `genesis_file_path` to point
  