get_build_artifact() tries to parse results as JSON, rendering non-Json artifacts impossible to download

Trying to download (potentially binary) artifacts via

```
jenkins_client.get_build_artifact("some_job", 42, "some-file.zip")
```

Results in errors like

```
DEBUG 2023-05-05 09:40:44 urllib3.connectionpool: https://base.url.com:443 "GET /job/some_job/42/artifact/some-file.zip HTTP/1.1" 200 17376
DEBUG 2023-05-05 09:40:44 charset_normalizer: Encoding detection: ascii is most likely the one.
Traceback (most recent call last):
  File "../site-packages/jenkins/__init__.py", line 731, in get_build_artifact
    return json.loads(response)
           ^^^^^^^^^^^^^^^^^^^^
  File "../json/__init__.py", line 346, in loads
    return _default_decoder.decode(s)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "../json/decoder.py", line 337, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "../json/decoder.py", line 355, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
```

This seems to happen because `jenkins/__init__.py` implements `get_build_artifact()` expecting JSON result:
```
response = self.jenkins_open(requests.Request(
        'GET', self._build_url(BUILD_ARTIFACT, locals())))

if response:
    return json.loads(response)
else:
    raise JenkinsException('job[%s] number[%s] does not exist' % (name, number))
```