Remove error logging when non-json response is received

[geoff-va]

When a request comes back with a status of ok but the response body is empty or not json, an error is logged.

This is deceiving because we have APIs that don't return a body - only a 200 or 201.

Example:

ibl_local_lms  | 2023-06-08 17:00:13,174 INFO 7 [ibl_request_router.views] [user 5] [ip 69.129.255.173] views.py:51 - Response core/users/platforms/: 201
ibl_local_lms  | 2023-06-08 17:00:13,175 ERROR 7 [ibl_request_router.views] [user 5] [ip 69.129.255.173] views.py:58 - Non-JSON response core/users/platforms/: 201
ibl_local_lms  | Traceback (most recent call last):
ibl_local_lms  |   File "/openedx/venv/lib/python3.8/site-packages/requests/models.py", line 971, in json
ibl_local_lms  |     return complexjson.loads(self.text, **kwargs)
ibl_local_lms  |   File "/openedx/venv/lib/python3.8/site-packages/simplejson/__init__.py", line 525, in loads
ibl_local_lms  |     return _default_decoder.decode(s)
ibl_local_lms  |   File "/openedx/venv/lib/python3.8/site-packages/simplejson/decoder.py", line 370, in decode
ibl_local_lms  |     obj, end = self.raw_decode(s)
ibl_local_lms  |   File "/openedx/venv/lib/python3.8/site-packages/simplejson/decoder.py", line 400, in raw_decode
ibl_local_lms  |     return self.scan_once(s, idx=_w(s, idx).end())
ibl_local_lms  | simplejson.errors.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
ibl_local_lms  |
ibl_local_lms  | During handling of the above exception, another exception occurred:
ibl_local_lms  |
ibl_local_lms  | Traceback (most recent call last):
ibl_local_lms  |   File "/openedx/requirements/ibl-edx-request-router-app-0.2.5/src/ibl_request_router/views.py", line 53, in manager_proxy_view
ibl_local_lms  |     response.json(), status=response.status_code
ibl_local_lms  |   File "/openedx/venv/lib/python3.8/site-packages/requests/models.py", line 975, in json
ibl_local_lms  |     raise RequestsJSONDecodeError(e.msg, e.doc, e.pos)
ibl_local_lms  | requests.exceptions.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

We've already logged the response as text, so there's no reason to log that the response wasn't json, I don't think. At the very least we should remove the exc_info=True from the log and it should probably be a warning and not error (since it's not an error - not every API is going to return a JSON body).