warning in plaid/exceptions.py:105

Running unit tests with pytest, I see the following warning:

```
.venv/lib/python3.12/site-packages/plaid/exceptions.py:105: DeprecationWarning: HTTPResponse.getheaders() is deprecated and will be removed in urllib3 v2.1.0. Instead access HTTPResponse.headers directly.
    self.headers = http_resp.getheaders()
```

https://github.com/plaid/plaid-python/blob/master/plaid/exceptions.py#L105