Regression with `AWS_WEB_IDENTITY_TOKEN_FILE` + `AWS_ROLE_ARN`

On obstore 0.4.0, I can use `AWS_WEB_IDENTITY_TOKEN_FILE` and the following works:

```python
store = obstore.store.S3Store("my_bucket")
obj = obstore.get(store, ".../file1.txt")

for data in obj.stream():
print(data)
```

On obstore 0.5.0, running the same code, I get this error:

```
obstore.exceptions.GenericError: Generic S3 error: Error performing POST REDACTED in 4.674430573s, after 10 retries, max_retries: 10, retry_timeout: 180s - HTTP error: error sending request

Debug source:
Generic {
store: "S3",
source: RetryError {
method: POST,
uri: None,
retries: 10,
max_retries: 10,
elapsed: 4.674430573s,
retry_timeout: 180s,
inner: Http(
HttpError {
kind: Connect,
source: reqwest::Error {
kind: Request,
source: hyper_util::client::legacy::Error(
Connect,
Custom {
kind: Other,
error: Custom {
kind: InvalidData,
error: InvalidCertificate(
UnknownIssuer,
),
},
},
),
},
},
),
},
}
```

Note, I get the same error on GCS.